Here are two places to start with distributed programming in Scheme:
Termite
Dimitris Vyzovitis’s patch for revision 8983 (of trunk) in PLT Scheme
Addendum 03/21/08
- Dimitris’ patch for additional mailbox functionality.
Addendum 04/26/08
Addendum 06/24/08
I’m pretty sure this patch has made it into the main source branch.