When the paladin's special mount dies, the paladin can't summon it for 30 days or when they level up, whichever comes faster. I understand it is so that the paladin can't abuse their mount as a meatshield, but I dislike the idea of waiting for such an absurd amount of time. Are there alternative ways for the paladin to faster regain their mount?
While the 3.5 revision did make things easier on the paladin—reducing the wait time to get a new special mount after a special mount dies from Third Edition's a year and a day (like a Third Edition and 3.5 familiar) to merely 30 days—, so far as I can tell, the game has no provision for getting back the same slain special mount in less than 30 days. I've found no prestige class that lessens this recovery time, nor have I found any feats, spells or special abilities, mundane or magic items, or other rules that lessen the recovery time from 30 days to something shorter.
This player would strongly recommend—if a PC paladin is reliant on his special mount—asking the DM to reduce this time or asking the DM to homebrew an alternative that would see this time reduced, eliminated, or mitigated (a new 3rd-level paladin spell that can briefly summon a slain special mount during the 30-day window sounds extraordinarily reasonable to this DM, for example). By way of argument, the druid—the game's most powerful class—can get back in 1 day his slain animal companion and the druid doesn't need it! This is so insulting to paladins (and, to a lesser degree, sorcerers, wizards, and other folks with a familiar) that just putting everyone on the druid's schedule just makes sense to this DM, player, and general reader. (Seriously, my inner game designer weeps at the game having three different schedules for recovery of slain and dismissed class-feature-granted creatures when a general rule covering all could've been formulated!)
Because this made me sad, I've offered below some options that, while they do not bring back from the dead in less than 30 days a slain special mount, may—with the DM's permission—get the paladin a brand new special mount in 1 day. Even if these options don't help in this situation, maybe they'll be useful later on or to other readers in a similar bind.
Multiclass with ashworm dragoon
The prestige class ashworm dragoon gains at level 1 the extraordinary ability ashworm mount that, in part, says, "If your ashworm mount is slain, you can obtain a new mount after a day of searching in any appropriate waste area" (Sandstorm 66). After a paladin/ashworm dragoon takes 1 day with his ashworm mount to complete the ritual Consecration of the Sifting Sand (67), the paladin can use the summon mount ability to bring forth his ashworm mount and the ashworm mount gains the benefits of being a special mount.
Combined, this means if an ashworm mount/special mount is slain, it takes a day of searching to find the ashworm mount then a day-long ritual to make it a special mount. However, getting the dead one still seems to require the normal 30 days. That is, this doesn't bring back from the dead a slain ashworm mount/special mount, but it may put the paladin/ashworm dragoon back in the saddle of a new special mount faster.
Take the feat Devoted Tracker
The feat Devoted Tracker, in part, says
If you have both the special mount and animal companion class features, you can designate your special mount as your animal companion. The mount gains all the benefits of being both your special mount and your animal companion. For instance, a 5th-level paladin/6th-level ranger’s special mount would have 4 bonus Hit Dice, a +6 natural armor adjustment, +2 Strength, +1 Dexterity, two bonus tricks, and Intelligence 6, as well as the empathic link, improved evasion, share spells, share saving throws, and link special abilities. (Complete Adventurer 108 and emphasis mine)
Note that the term benefits here is undefined. Further, note that, although the example gives some indication of what may be meant, examples aren't rules and don't necessarily cover everything. This means that a shaky argument can be made that one of the benefits of the devoted tracker's special mount sharing the abilities of the animal companion is the ability of the devoted tracker to, like with a dead animal companion, get a new creature—an animal companion/special mount—after the previous one's slain if the paladin just spends 24 hours in prayer.
This reader suspects that were the campaign managed by, for instance, an ungenerous computer program, this totally wouldn't fly, but by plying a human DM with beer and pizza—and carefully explaining how this cost the PC not only an extremely precious feat but also four paladin levels so that the PC could even have an animal companion via the ranger class!—, such an argument might work with a DM who is otherwise loath to bend the rules yet still wants to see the player happy and the PC resume his place in the party.
(One level of druid or another class with an animal companion could be substituted instead of ranger if the feat's prerequisites are still met, but then—according to the rules—the PC can't take further paladin levels, and the feat Devoted Tracker allows the PC to multiclass freely between paladin and ranger. The rules for ex-paladins should also be a topic of conversation with the DM but should be saved for another time!)
Release from service the special mount and summon another
The spell-like ability special mount, in part, says that "the paladin may release a particular mount from service (if it has grown too old to join her crusade, for instance)" (Player's Handbook 44). Again, while the example provides a reason that a paladin may dismiss the special mount from service, it's not inclusive. Thus, if the DM allows the player to track the special mount's hit points, when the special mount will be slain by the next attack—sticking the paladin for 30 days without a special mount—the paladin releases the special mount from his service.
How the paladin releases a special mount from service isn't clear from the text (see this question), but assuming it's not a ritual that takes months and, instead, a whenever-the-paladin-wants kind of event, releasing from service such a special mount will see the paladin's special mount become a normal mount then—if it's hp are low enough—immediately die because of its now-further-reduced hp. (The special mount can lose as many as 8 Hit Dice in the process of being released from service!) This may leave the paladin beneath a dead horse, but when he regains a use of his summon mount spell-like ability (see this question) the paladin can call a new special mount: see, the paladin's special mount didn't die, that heavy warhorse over there that used to be in the paladin's service died, and, while that sucks for that heavy warhorse, at least that means the paladin can continue his holy war against evil tomorrow, albeit astride a different special mount.
This is not the sort of thing this player would spring on a DM, and this DM would look askance upon such a event were it sprung on him, but it is a hole in the rules that the DM needs to fill, and, to this reader, filling it in such a way so as not to hose the PC paladin seems better for the game than the alternative. Nonetheless, I strongly urge discussing how a special mount is released from service before attempting this.
Note: It saddened me that the Player's Handbook II rules for Class Feature Retraining don't include on Table 8.2 changing the paladin's special mount (192–3). However, if those rules are used in the campaign, pointing out to the DM that the table includes a wizard's familiar may persuade the DM to allow a new special mount upon leveling up instead of a different retraining option. This may not lessen the time from 30 days if levels take longer than 30 days to gain, and it won't bring back from the dead a slain special mount, but it may get the paladin back in the saddle faster.
I'm not an encyclopedia of the 3.X books, but I do not believe that there is a RAW way to gain the mount back prior to one of the two stated conditions being met. I can confirm that there isn't one in any of the core books or Defenders of the Faith.
Depending on the paladin's current XP it might be faster for them to find an item monster or spell that causes them to lose a level (setting their XP to half way through their new level) and then gaining XP to get back to their original level.
An extension of the "level loss/gain" above would be for them to die and have the Reincarnate spell used on the paladin. This would cause a level loss (and likely a race change). Overall I wouldn't recommend going down the lose/gain path, but it is the only option to expedite this according to RAW.
As Patrick mentions in the comments there are plenty of spells that could revive the mount, but those don't allow the Paladin to summon it any faster, they just remove the need to do so.
Special mounts range from utilitarian tools to cherished family members depending on the PC and player.
If the mount is simply a tool to the player, it probably isn't all that unbalanced to simply allow them to summon up another one. Few (no) classes have part of their kit locked out for 30 days when they fail at something. Some minor cost to discourage shenanigans with sacrificing an infinite stream of horses might be required based on your group's temperament.
If the mount has emotional value to your story there's nothing wrong with offering an adventure hook of some sort to expedite the mount's return. Maybe the paladin can sacrifice something else of value, journey to a forgotten temple, or otherwise appease their god.
Overall there's not much mechanical value to forcing them to wait 30 days. This isn't really in line with other classes' abilities. If it were my campaign I'd probably try and come up with an interesting plot hook rather than some sort of monetary cost and allow them to get the mount back prior to waiting a full month.