I was an intern in a congressional office, and I can say this is partially true. Letters do get delayed, but we tended to get them a few weeks after they were sent, not a few months. And we do log, file and respond to all letters, though I don't know what (if anything) gets done beyond that. A LOT of non-identical letters- i.e. not something that a lobbying group sent you to mail to your congressman- will make a difference. However, it is definitely true that phone calls and especially office visits are a lot more influential. A small group coming to the office (especially if they represent a larger constituency) usually gets to meet with a staff member for a while and get their message across. If you're going to do this, my only advice is to be completely prepared (and not drunk--this has happened more than once). If you know your issue and can explain it in a persuasive way, it can actually change the minds of the staff who have the ear of the representative. Don't expect much if you disagree with the rep on a major issue though. If it's something where the rep has a staked out position with a long history, and you disagree with it, we'll certainly listen but that's about it. Basically, pick an issue without too much history and where the congressman might agree with you with some prodding, and you can actually get results.