I got these mailing addresses for John DiMaggio from http://www.fanmail.biz/7614.html , so I'm not sure if they will work or not. If you write to him, please let me know if you did or didn't get a reply, and I'll post it here. It's a good idea to enclose a self-addressed stamped envelope with your letter, if you're hoping for an autograph.
John DiMaggio
c/o Barry Katz Management
1776 Broadway, Suite 2001
New York, NY 10019
John DiMaggio
c/o The Gersh Agency
232 N. Canon Drive
Beverly Hills, CA 90210
If anyone knows of any more contact addresses, please let the club know.