Rich Piotter has an 8-motor / 4-leg walker (Spyder)
and another 8-motor / 4-leg walker (Quadrapod) page
For a very advanced bit of inspiration, there's
an interesting page up about an 8-legged robotic
scorpion (24 motors!) project here.
Sebastiaan van Vliet has a lot of interesting
information up on his ongoing 8-motor / 4-legged