Just discovered this service and I am absolutely amazed at how easy it is. This is just a test screencast but I can definitely see myself using this service in future.

It is fully integrated with posterous. I go absolutely nuts for stuff like this. Ease of use and simplicity. That's why I adore posterous. Screenr automatically converts the screencast to web and iphone versions. You further have the option to convert it to a Youtube video as well or to download the mp4 version of it. You have the option to automatically post it to twitter or to embed it on a website. Best of all, it is free! Only limit is that 5 minutes per screencast. A handy bookmarklet is also availailable.