I recently built a 14x16 shed that is being used by my wife for office, but it would make a fantastic workshop (A point I bring up with her quite often... ). It is framed primarily with 6x6 timbers (the tie beams are 6x8). A picture can be seen here: http://www.tfguild.org/ubbcgibin/ultimatebb.cgi?ubb=get_topic;f=9;t=000021
The design is by Jack Sobon.
Cheers,
Dan