Best "side-band" of all time

MD. 45 (Dave Mustane's side band, only recorded one record)

A Perfect Circle.Engrish_Major

Temple of the dog deserves a mention here.. don't know about best but damn good.

Temple of the dog

There are otherr ones I've listened to but I can't think of them at the moment.

Yeah, Temple of the Dog for me, either them, or liquid tension experiment.AxeStrangler

Superjoint Ritual

Gravediggaz comes to mind for me...

Made up of RZA from the Wu-Tang, Prince Paul of Stetsasonic and De La Soul fame, Frukwan of Stetsasonic, and Too Poetic.

"Nowhere to Run, Nowhere to Hide"