Classes, templates, and feats
Surreal's Lists of Stuff mentions—and A_soo's answer describes—many of the classes granting wild shape and its alternatives. (Omitting, for example, the variant totem druid (Dragon #335 87) is totally acceptable: the level 1 supernatural ability totem shape "uses all the same rules as wild shape" but isn't actually called wild shape. Sigh. Good thing that doesn't matter as druid levels are off the table anyway.) KRyan's answer describes the feat Initiate of Horus-Re (CV 31) with its limited wild shape and the template Mulhorandi divine minion with its variant fast wild shape.
In addition, the prestige class shapeshifter (originally Oriental Adventures 45-6 and updated to Dungeons and Dragons 3.5 by the Dragon #318 article "Oriental Adventures Update: Eastern Flavor" (35-6)) grants explicitly and progressively better wild shape starting at level 1. In addition to the requirements base attack bonus +3 and Concentration 10 ranks, a creature needs to meet the special requirement Alternate Form: "Must either know polymorph self or have a natural alternate form, alter self, polymorph self, or shapechange ability" (OA 46). Despite polymorph self not being a spell in 3.5, the update left that untouched; talk to the DM and see if "minor adjustments" (DMG 4) can be made to these requirements (like expanding them!) to bring them in line with the 3.5 revision.
The planetouched race worghest (Dragon #350 56-7) has the supernatural ability change shape allowing it at will to take a standard action to assume the form of a wolf but also allowing it to "take feats requiring the druid's wild shape ability as a prerequisite." This makes available options that should only be accessible to creatures with actual wild shape—like Aberration Wild Shape (Lords of Madness 178) or Bestial Charge (Complete Champion 56)—which might make druids perceive a worghest's already supernatural ability change shape as wild shape. Maybe this is close enough?
While a worghest normally mandates a Level Adjustment of +2, a generous reading of Player's Guide to Faerûn on Variants: Races with Level Adjustments (190-1) lets a planetouched creature change its type from outsider to humanoid (planetouched) to suffer no Level Adjustment, but it's likely only by accident that these rules apply to the worghest, so ask the DM and good luck. Also, like many creatures that can assume other forms, changing from wolf to worghest may be an issue.
The Dragon #324 Magic Shop column "Power at a Price" includes the following:
The Skin of Kaletor
This bearskin cloak… gives off a powerful rotting stench that is immediately noticeable and incurs a −6 penalty on all Charisma-based skill checks and wild empathy checks. When wearing a skin of Kaletor, a druid can use the wild shape ability as if he were four levels higher than his current druid level. Additionally, any non-druid who wears the cloak can use the wild shape ability once per day as a 4th-level druid.
Faint transmutation; CL 4th; Craft Wondrous Item, creator must be a druid; Price 12,000 gp; Weight 10 lb.
Obviously, this item has problems—it's a little heavy, don't you think?—, but chief among them is that a level 4 druid doesn't have the supernatural ability wild shape; given the skin's drawback, a DM should forgive this oversight and house rule the skin to level 5. If the DM doesn't, the amulet of wild shape (Magic of Faerûn 167) (40,000 gp; 0 lbs.) grants wild shape as a level 5 druid… or increases existing wild shape ability by 4 effective druid levels to a maximum of 20. The amulet's advantage is that it's not limited to once per day like the skin, but the skin's not limited to an effective druid level of 20. O, the skin has the advantage of lower price, too, if that's a concern. (Ask the DM what happens if a creature gains a level while wearing a borrowed skin, takes the feat Extra Wild Shape (Complete Divine 81) (or willfully misreads Fast Wild Shape (CD 81-2)), then returns the skin to its owner. I suspect the creature's head explodes and it dies but results may vary.)
(Combining amulet then skin with the druid's vestment (DMG 268) (10,000 gp; 0 lbs.) and the magic item set trappings of the beast (Complete Champion 135-6 et al. collectively costing over 50,000 gp) lets the wearer use wild shape like a level 10 druid except that it's 6 times per day and that it's usable as a swift action, which is pretty cool, and it had better be cool: the whole shebang costs over 100,000 gp!)