Trading coding for designing

Does anyone know of any site where a programmer who knows his limitations as a designer can get in touch with a real designer to have a site design created? I'm looking to trade my coding skills (say building the backend for a site, or performance tuning a site) in exchange for the work done. I'm not looking for a partnership or a joint venture or anything, just a one-off straightforward exchange of skills and time... Thanks for any pointers!