Screenjelly is a great site to use for creating screencasts. It is very user friendly and has the ability to upload to a number of social networking sites, such as: Facebook, Twitter, Stumble Upon, etc. Users of Jing will feel right at home w/ how simple it is to record what's happening on your screen.
I think what makes SJ such a great solution for people who don't want to spend a lot of money on a screen recording app, is how simple it is to use. Just click the record button and select which way you want to share your video, Twitter, email, etc.
The one aspect missing from SJ which I think would make it a huge success is the ability to generate an embed code, so users can add it to their site/blog. However, that being said, I think Screen Jelly is a great app for what it does and definitely worth a look.