Hi all -
I consider most of the WotC line to be core and available. Such new magic systems as Incarnum, Tome of Magic and Psionics are not of interest to me and thus aren't books that I've even considered picking up.
Races of the Dragon has spells that are overly powerful and thus isn't allowed. Book of Nine Swords is revolutionary but is something that I'm considering.
The Environmental books by Fantasy Flight Games are very good, detailed and came out long before WotC's and thus I use them extensively as the DM.
Green Ronin's Advanced Bestiary, Players Guide, and Game Masters Manual are by Skip Williams, KC Owens, and other veterans of WotC. With Skip writting the Players Guide after being the Sage for 20+ years I think he has what it takes to know the game well enough to warrant inclusion into my allowed resources.
Kenzer & Co has their Kalamar Setting with the D&D logo. They paid good money, have to have everything signed off by WotC to have that logo. Meaning that their KoK Players Guide is very well suited and viable. I use their Dangerous Denzions as much as I use the MM II-IV.
Necromancer Games has several books that I consider to be valuable as a DM - such as Grimtooths - although it is a very easy conversion from the originals as they were mechanics independant. Tome of Horrors I is very good, but Creature Collection I-III isn't.
For module design of course Dungeon comes to mind, but so does Rob Kuntz's adventures. I'm running his Cairn of the Skeleton King and a skeleton is an easy conversion to 3.5 from his generic system. And with the Monster Manual I-IV, Dangerous Denzions, and other monster books, I no longer believe that monsters are important to the concept of the adventure. All an author needs to give me now is the design and layout and monster concept - a ghost like being (important lvl drain, energy drain, incorpreal, etc...).
Well that's my rant.
Be Well. Be Well Considered.
Theocrat Issak