I just released a tool called Microliner that lets you outline your conversations on Twitter.
I don't think anyone has ever had a tool like this, so I'd better explain how it works.
1. Open up the Microliner Workspace window. Enter an idea. 140 characters or less, please. :-)
2. Click the Tweet button. It goes out to all your followers on Twitter.
3. Wait a minute or so. Click the Replies button. Microliner calls Twitter and gets the replies, and arranges them under the messages they are in response to.
4. You can then reply to the replies, and so on. Once you get going, you can participate in a dozen conversations at once, and not lose track of where you are or who you're conversing with. It really works.