screenr.com that allows you to create a screencast and post it to Twitter. The Screenr program allows you five minutes of recording, pre-set or custom screen size capturing, integrated audio, and a bookmarklet to record anytime. Each screencast sits on an individual URL and the service provides you the embed code to share the screencast. The service provides a reTweet function to send the link out, but fails to capture the Twitter conversation. I found the Screenr program easy to use and I did not need to download any software.
Here is a quick example of one of my screencasts from Screenr, http://screenr.com/r0S