I know that everyone of us can take advantage of this, because we are all playing on these machines daily.
According to the lawmakers I deal with the letter is the most noticed communication they receive. Phone calls depend on an aide relaying the tone of your wishes, e-mails are so numerous they are easily missed, but regular old mail is as good as face to face if done properly.
What is proper? Business format, polite, direct communication in brief first paragraph (executive summary), more in depth discussion in body.
With computers we all have the opportunity to write a letter to our legislators and leaders. We can write one letter to one person, print it, then go back in and edit it for the next. This way it is not just a basic form letter sent to everyone.
Make sure to remain polite, clearly state who you are and your contact information, be clear and concise with your comments and requests, limit the number of issues per letter (don't make it a "Christmas wish list") ... and, did I say be polite?
Use your computer, invest in nice paper, envelopes and stamps, and let your leaders know who you are and what you support.
I will let those I write to or visit with know some of the organizations I belong to, but when it comes to citing facts I go back to the original source rather than quote NRA, GOA or others. Our leaders put more stock in someone that takes the time to do their own research or verification than someone that just spews someone else's words.