Aside from what has been mentioned, the environmental books (Dungeonscape, Frostburn, Sandstorm, and Stormwrack) all have excellent rules and stats for many different things. I'm rather fond of Dungeonscape because it has the factotum in it which is perhaps the master "jack of all trades" class. In the "Adaptation" description it literally says Indiana Jones was a good example of a factotum, minus magic and plus guns of course.
The Completes are usually pretty good, though Complete Psionics is essentially nerfs with a cost which means pretty much everyone avoids it. Martial melee characters love Complete Champion because it gives the barbarian an ACF that trades the +10 movement speed for Pounce and with various other things in 3.X can lead to a character doing 6,000+ damage in a single round at level 20.