Psion
Adventurer
Your best bet is to pick up the three PS pdf's for $15.00 (if you live in the US). That expands upon the outer planes. The MotP outer planes descriptions are basically a capsule version of the 3 PS boxed sets converted to 3e.
Oh, and for those "other deities" things, that refers mostly to the deities of nonhuman races (deities of the elves, dwarves, etc.) Most of them are in the current incarnation of the idea sponge that is FR, though they were originally Greyhawk / AD&D 1e and appreaed in the 1e Deities & Demigods and Unearhed Arcana (and dragon articles before that.)
Actually, now that I think of it, combined with the Hell articles someone else mentioned, you may find the Dragon anothology CD a good resource as well if you can get a hold of it. (Though much of the hell article was reproduced in the planes of law boxed set.)
Oh, and for those "other deities" things, that refers mostly to the deities of nonhuman races (deities of the elves, dwarves, etc.) Most of them are in the current incarnation of the idea sponge that is FR, though they were originally Greyhawk / AD&D 1e and appreaed in the 1e Deities & Demigods and Unearhed Arcana (and dragon articles before that.)
Actually, now that I think of it, combined with the Hell articles someone else mentioned, you may find the Dragon anothology CD a good resource as well if you can get a hold of it. (Though much of the hell article was reproduced in the planes of law boxed set.)