FreeNAS and Couchpotato
A good guide is available here: Freenas 9.2.0 with Transmission and Couchpotato/Sickbeard as a DLNA-Server
Transmission
[How-To] Transmission & FreeNAS Shared Mount Points
There is a great tutorial on how to set up FreeNAS with Transmission on the FreeNAS forums: [How-To] Transmission & FreeNAS Shared Mount Points