Here's one that I built in Bricksmith some time back, but just recently got all the right parts to build it for real.   It uses a simple leg mechanism that was mostly just an excuse to use those cool bent liftarms in old brown.  And, of course, some cheese slopes.

Tags: 

Lego 
Technic 
Power Functions
MOC
Spider
Arachnid
Robot 
Walker
Kinetic 
Sculpture
Toy
Blue 
Brown 
White
Bley

Links:  

Photos: http://www.flickr.com/photos/arcanemettles/
Video: http://www.youtube.com/watch?v=qmEnDZqLJT4
Ldraw File: http://www.brickshelf.com/cgi-bin/gallery.cgi?m=telecasterman