There's
Arcana Unearthed, by Monte Cook, which is the "alternative players handbook" with new races (giants, litorians, sibbecai, faen etc.) and alternative classes (mage blades, runethanes, greenbonds etc.) and a raft of slightly different rules.
It came out at about the same time as 3.5, and was later updated to
Arcana Evolved, with a new race, a new class, evolved levels, new spell templates and colour pictures.
Then there's Unearthed Arcana. Originally, of course, a Gary Gygax supplement for 1st edition that introduced the Barbarian, Cavalier, PC Drow and an essay on pole-arms (amongst others). Monte's book was named in homage to this, with an understanding with WOTC that (a) he could use it and (b) they wouldn't be needing it.
But then they put out Unearthed Arcana (3.5 edition), a compilation of variant rules (all of which are on the online SRDs).
And just to muddy the acronymic waters there's also a d20 modern supplement called Urban Arcana, although it's usually obvious from context which UA you're talking about.