Here are some of the best places I have found:

SolarBugs Tutorials, Information. He sells a lot of good stuff (SolarPanels, 1381, Fleds, Caps, etc) at GREAT prices.

Probably, the best All-Around place to find components for your creations.


The Robot Room

David Cook's personal site. Info on his robots and projects. Home of Sandwich, the line follower.


Home of Maxibug, SPAI, MicroHexapod and other interesting creatures.



Bruce Robinson webpage. Really nice circuits, articles, and ideas. Check out Hider.


PCB designs for all kind of BEAM circuits.
http://www.philohome.com Nice place to look for some ''almost advanced'' home-made sensors for the Lego Mindstorms.
SunEater circuits, Photovores, and more.