I'll nominate Paizo: Their page count per price can't be touched and atleast 24 d20 releases for the year that consistantly have something for all styles of players and DM's.
Their web support, which includes free modules, free maps, free graphics, and now effective rules guidance and DM advice. Pretty outstanding in the big picture. By the way, they are also one of the biggest d20 material producers, if not the biggest.