Napftor
Explorer
I'm pretty keen on Tricky Owlbear's Behind the Spells: Compendium (for obvious reasons) which is still easily found in print at Lulu and in pdf form at your favorite online venue like here! All reviews have been quite positive but sales a bit slow given the book's emergence during the launch of 4e (so I hope you don't mind the blatant pimping here).