Of the electronically mediated kind.
The Cause Caller site give you tools for setting up a "virtual phonebank" namely auto dialing software for contacting politicians and a wiki to provide callers with a script for guide their phone calls.
I used it to set up a page people can use to call Senator Obama's Senate and Campaign offices to express their disapproval of the FISA "compromise" that lets telecom companies off the hook for helping President Bush spy on us.
So far the response has been a little underwhelming, only about 6 calls or so generated, but I'm going to see what happens.
If you would like to give it a try, click this link to go to the page I set up. Read through the script, then enter your phone number in the box provided and click "start calling." The site will call your phone, then connect you to the first office. Stay on the line when they hang up and the site should connect you to the next office.
Thanks for the help!