Screenr is paired with twitter, so you'll need a twitter account to save any screen-casting you complete. There is an option to tweet the finished screen-cast, or post and share like other Web2.0 tools. Go to screenr, find the record option, and follow onscreen instructions. You are limited to 5 minutes, but isn't that a long enough time to watch a "how to" video?
Follow up on 3/23/11: Screenr is now allowing you to pair your login identity with Twitter, Google, Facebook, Linked-In, Yahoo, and Windows Live.