Are there any good official resources (racial feats or class substitutions) for Lizardfolk characters in 3.5? Races of Eberron threw goblinoids and orcs a bone but nothing for the poor denizens of Q'barra. I'll be playing in Eberron but non-setting specific resources are fine. I don't imagine there's much but there's gotta be something and I'm having no luck finding anything.
Beyond BESW's answer of Savage Species and Serpent Kingdoms containing mechanics that can be employed by lizardfolk but aren't exclusive to them
There's Very Little
Few attempts were made to make Dungeons and Dragons, 3rd Edition lizardfolk interesting, which is kind of a shame, really, for an iconic creature with over 30 years of history.1
- The Player's Guide to Faerûn contains the regional feats Axe Thrower (33), Dauntless (37), and Tireless (46), which, while not exclusive to lizardfolk, are restricted to characters from specific regions, and one of those regions is the civilized lizardfolk marsh city of Surkh. These are... actually pretty good for the right characters, except the feat Dauntless; don't take that.
- Dragon #334's article "Ecology of the Lizardfolk" (52-7) has the lizardfolk-as-a-prerequisite feats Chameleon Blood (56) and Reptilian Healing (57). Both are... unspectacular.
I am unaware of any lizardfolk racial substitution levels published by Wizards of the Coast.
In fact, even DandDWiki lists no entries for homebrew lizardfolk racial substitution levels. There are a few 3rd-party products for those who want more lizardfolk crunch. Mongoose's Slayer's Guide to Lizardfolk contains 4 feats, none of which are exclusive to lizardfolk, and the lizardfolk-exclusive prestige classes stillguard and scaled king, both of which are unimpressive. Paradigm Concepts published Ssethregore: In the Coils of the Serpent, an entire empire ruled by non-product-identity lizard types, for the Arcanis setting; Ssethregore apparently contains feats, prestige classes, and so on, but I've not seen it--maybe someone who has could Comment on it.
In the Player's Handbook (1978) the 7th-level druid spell reincarnate (64) and the 6th-level magic-user spell reincarnate (85-6) could bring a dead character back as even a dryad (!) or an ogre mage (!!), respectively, but neither spell could bring a dead creature back as a lizard man (calling them folk came later--hey, it was a different time). Despite this, the Rogue's Gallery (1980) had Jeff R. Leason's character Phoebus (44-5) brought back from the dead as a lizard man; Jeff Dee's illustration of ol' Phoebus wielding a trident captured my 12-year-old imagination. But I did always wonder how that happened when that actually couldn't be rolled.
In Dungeons and Dragons 3.5 there's only a 1% chance a creature who's the target of the 4th-level Drd spell reincarnate [trans] (PH 270) gaining a new young adult lizardfolk body. There's a higher chance of getting a kobold body than a lizardfolk one. But, y'know, at least there is a chance.
The "Serpent Kingdoms" book (early 3.5, with lots of 3.0 relics) has some features for lizardy folks. It's poorly laid out so it's hard to be sure, but I don't see anything specifically for lizardfolk; instead it's got options for "Scaled Ones," which is a generic term for sapient serpenty peoples including lizardfolk. Mostly it's got a handful of feats, but there are also some amusing equipment options for Scaled Ones.
The 3.0 "Savage Species" manual has some more useful-but-nonspecific features which lizardfolk can take advantage of via their more generic racial features like natural attacks. It is 3.0, so some of its mechanics will need massaging in order to fit a 3.5 campaign.