I'll give it a try, I'm going to sit down now and think about what rocks about my web app (ahh, sod it, it's http://tweetingmachine.com), what makes it relevant to the people I contact, and why it should be covered. Thanks!
However, I think you might have two minor problems here:
1) Getting people on the site and let people know you exist. See rmah's suggstion above. Free accounts for bloggers is a good idea at this stage, but not enough.
2) Customer acquisition: Please tell me immediately _how much_ I am going to spend. I won't hook my twitter account with your app, I've come to know your site 10 seconds ago, I won't let you dive through my contacts. I don't even know if this is a paid or a free service. To me this is a enough to let me close the browser tab and look away.
I'm now following the advice and have spent a good amount of time today finding relevant websites and contacting them about TweetingMachine. If all goes to plan I hope to write a successful post here in a couple of months stating everything I did.