My favorites so far have been 'cerulean seas', 'psionics unleashed' and 'strategists and tacticians'
Cerulean Seas because I love the idea of a completely underwater campaign
Psionics Unleashed for the obvious reasons
Strategists and Tacticians gives characters of all classes more varied...
Wow. Thanks for all the replies and advice. Didn't think to mention that we are not power-gamers, but I see your point there. I believe I'm going with Warlock as the main class and adding Binder levels for flavor. That will add some interesting abilities into the mix.
I was considering a multiclass Warlock/Binder for my new character and I was wondering if anyone here had experience with that class combo. Thanks in advance for the advice.