Barbarian is frequently cited as an excellent 1-level- or 2-level-long class. When the wizard can use the 2nd-level spell rope trick [trans] (PH 273) to make the adventuring day 15 min. long, a lone rage per day is acceptable,1 but until then—or if on a clock or if the party is without a wizard for some reason2—one rage a day just isn't enough.
What ways are available to a creature that can normally rage but once a day to rage more often without taking class levels or feats?3
The cheap is preferred over the expensive, the obvious over that necessitating DM intervention, the official over the third-party, and the published over the custom-made, but I suspect options are so few (mostly magic items and spells) that this list can be inclusive without being excessive, so any sources are acceptable. Finally, Pathfinder changed how the barbarian's rage functions, so options from that game are probably unacceptable.
If it matters, my character is currently a barbarian 1/fighter 1/ranger 1/totemist 1 who ends up with an even wilder array of classes by level 20, but will only ever have a Use Magic Device skill bonus of +3 and no other spell list but the ranger's. Other party members are a bard, a binder, a beguiler, a shadowcaster, and a warlock (hence the need for more rage). The other party members are experts with the skill Use Magic Device, and, if I need rely on them to do so, they can use on my behalf just about any magic item.
1 Or, more appropriately, the rage variant whirling frenzy, as that's what my character has.
2 Such as in a campaign like the one I'm in wherein players agree to play classes of Tiers 3 to 6. (No, nobody's multiclassing into commoner.)
3 For example, the feat Extra Rage (CW 98), the prestige class totem rager (MoI 153-7), and the prestige class runescarred berserker (Una 31-2) don't do me any good; I've classes and feats picked already. I already know that a custom magic item that grants the feat Extra Rage has an estimated cost of between 10,000 gp and 20,000 gp (AE 128), so don't include that.