Professional Services can be broken up between many different things: medical, accountancy, legal, architectural, and so on. From these, each as well, branch off into their own sections:
Medical:
Orthopedics
Chiropractors
Doctors/Nurses
Legal:
Courts
Attorneys/Assistants
Taxes (Forms/Returns/etc.)
and it stems out from there. These are services either provided by large corporations or certified/accomplished individuals serving the community and better businesses.
In barter, you'll have access to many of these features and more!
“The certificate club has helped me get my business up and going with little money spent. Thank you!!”
-John Gallie, owner of JTG Systems