FWIW, since people don't seem to know this: Dead tree letters >> phone > fax >>> email >>>>>>> any online petition, in terms of how motivated staff are to convey your sentiment up the totem pole. (Anecdotal from brothers' service with a few congressional reps.)
[Edit: Sorry, checked on my screen but didn't realize my resolution was too high to show me if it broke lines.]
Generally I've had no issues getting meetings, at least with a staffer, of my congressperson.
On a sidenote, does a group that focuses on gov't relations and PR exist that represents what would is largely the consensus HN community interest - i.e. making the case to elected officials and the public what sort of laws would improve prospects for technical innovation. The EFF focuses largely on digital civil rights, but that certainly isn't the only realm where Washington, Sacramento, Albany, etc. affect us.
I'd be really wary unless it had a very very focused mission. I think there's a lot of diversity among HN readers, and I hate being a part of organizations which claim to speak for me but end up supporting things I oppose, etc.
Right now, I think the startup visa thing and opposition to new stupid laws like sopa/pipa is all I have mental bandwidth to care about.
[Edit: Sorry, checked on my screen but didn't realize my resolution was too high to show me if it broke lines.]