The idea of collaborating with other artists appeals to me for several reasons. Collaborations offer an opportunity to begin a piece and hand it off to another artist to complete. Conversely, you receive a piece begun with someone else's vision, and figure out how to incorporate your aesthetics into theirs to make a piece with a unique dual voice. There are challenges, too. There is a weight to "get it right" when someone else's work is involved. It's helpful if you have philosophical common ground with the other artist, but it stretches you more if your aesthetics are somewhat different. 

So far I have collaborated with two artists: acrylic/mixed media artist Janice Kindred and clay sculptor Victoria Kile. When I collaborated with Janice, we did two 12x12" pieces.She began one, I began the other, we traded midway through, and were both happy with the outcomes. These paintings went quickly for us both because Janice and I have similar working methods. The pieces I worked on with Victoria were more challenging, because clay sculpture is more foreign to me. I think she felt the same way about one of the assemblages that I began and handed off to her. We collaborated on four pieces and were both satisfied with them eventually. I'd recommend this process to any creative who is in a slump. I promise that it will stimulate and enlighten you.