Tennis Message Boards
Due for forum URL's changing some of the links below will take you to the general website which provides a link to their forum.  If you have a forum to add to the list please let me know.

Tennis4you.com

ChatTennis.com
ESPN.com
Jeff Coopers Tennis
Kings of Clay
Mens Tennis Forum
Talk About Tennis
TennisNet.org
Tennis Week
Tennis-X
Yahoo Tennis Forum