In addition to my previously stated Facebook vision..
The letter application could be launched simply by a link at the bottom of a story or a Web page, or maybe a text box (similar to the L-J World comment box scheme) could also serve as a jumping point for a letter. While I prefer the idea of a pop-up box, getting somebody to type something the minute they think it could mean a more potent thought.
There are a few approaches when it comes to finding the recipient(s). Perhaps the user could type in their state and the a pop-up box could categorize recipients (choose from congressmen, newspapers, etc.) Or, the user could type in their state and the names of recipients, which would be matched by a database of the names typed in. More of what I see is drop-down boxes.
For example, select “newspaper” in a drop-down box, and another box will let the user see major publications within an x-mile radius. Or, select “congressmen” and choose a congressman through the subsequent drop-down box.
As for the letter itself, I’m behind Nate’s idea (iterated by Courtney). An approach that is initially objective is the best way to get the letter read, anyhow.
As far as setup goes, I’m of the opinion that the letter should be typed and THEN recipients chosen (as not to clutter the user’s thought with choices).
Another important element, as I mentioned earlier, is the implementation not necessarily into a social network (though this would be a totally kick-ass and effective method), but allowing your friends to see what you’ve written and give them a chance to put in their two cents (or however much time they’re willing to take out of their day/spend on postage). Perhaps a “share this with your friends” button?
The “share this with your friends” approach is a little weak – typing in e-mail addresses of people you think would care is defunct. (This is why a social network implementation is the best cheese with the cracker. Easy interest for the easily amused!)
The most important thing that we have to consider is that people need to be enthused to use this application. We need to create it ergonomically with a big hook.. it can’t be too daunting. And it must be pretty. Very pretty.
And, of course, the user should be able to print or e-mail the letter to whomever they choose.
Ta-da!