Sorry, I haven't got very far on this page.
Posted some some very good links that I use alot:

A lifesaver from Amsterdam. Here you'll find a huge archive of all Lego set's, with scanned images of every building instruction imagineable.

Visual Basic? Guillermo Zaballa has made a RealBasic class for adding RCX support for applications. Only works for Serial IR-Towers.

VLL between RCX and Microscout. Documented on Ton Ton's Project pages, you'll find full instructions on using VLL (Visual Light Language)

Inspiration:

Markus Materns - Macs Robotics Page. Contains very good building instructions and inventive models.

Lego Mindstorms Monthly. Newsletter for Lego Mindstorms events.

Kevin Clague's Lego Pages. Author of several Mindstorms books. Also has some excellent LDraw tools.

Mario Ferrari - Also an author of a Mindstoms book, with loads of models for inspiration.