It is my understanding that contacting via non-form letter is the best way to reach your representative. This comes from a chat with a friend who worked as an assistant in a congressional office; she said form letters were discarded, phone calls were usually from a few select cranks who called every day about the same esoteric issue, and custom letters were read and their contents summarized for the congressperson.
A (legible!) hand-written letter would probably fare even better ... as it shows that you care enough about the issue to take the time to write it by hand.
One of my room mates discovered this trove of comedy gold and has been signing up all his friends to receive them. They're actually pretty convincing, although they lack the indentation marks one would expect to see from a real pen.
Andrew Mason (of groupon fame) had an observation a few years ago at startup school that says activism is currently how long someone will inconvenience themselves. The longer the inconvenience and the more infrequent, the more seriously it's treated.
