Here’s a site specializing in listing remix contests. “Reeemix.com provides you with a continuously updated link list to remix contests worldwide.” Looks like an excellent resource.
Thanks to Laurent for this tip. He also says: “I’m looking for fellow producers to work with.”
If you are looking for other producers, many of whom have been known to collaborate with others, I can highly recommend ccmixter.org. Or if you want to get in touch with Laurent directly, you can do so via his myspace space referenced in the link above.