Oh, yeah! The Advanced Bestiary and three Master class books by Steve Kenson (i.e, Psychic's Handbook, Shaman's Handbook, and Handbook), along with Artificer's Handbook (Mystic Eye Games), Book of Templates (Silverthorne/Goodman Games), Book of Iron Might (Malhavoc), WOTC's Unearthed Arcana, and Poisoncraft (Blue Devil) are the cornerstone of my non-core DND supplements and my house rules/tweaks (along with Sean Reynold's Fewer Absolutes. Based on the Trailblazer preview, I think Trailblazer will be a new addition to the list.
Green Ronin's Book of Fiends (for the Thamaturge and inspiration), Book of the Righteous (for the Holy Warrior and just inspiration), Cavalier's Handbook, and Unholy Warrior's Handbook are also great.