Th. GRP Editor (trans)
A better, more precise, button controlled sprite/bg editor. (Author: Th. Translator: LohadL)
Random's Big Dumb Library + Map Editor
A bunch of functions that might be helpful? Also a map editor.
eZSB Toolkit: SmileBASIC Made eZ
Helps makes games easier and quicker than ever before! Even in 3D (MODE 7)
V360 Grab Bag
A bunch of random stuff. Tech demos and development tools! Even a semi-functioning graph calculator