Screenjelly is a quick screencasting web tool that records your screen activity with your voice so you can share it as a video via Twitter, email, or other bookmarking services. You can use it to quickly share cool apps, software tips, report a bug, or just show stuff you like. To start recording, click on the red button, full screen recording starts after 5 seconds, with 3-minute limit. No need to install or download anything!

More info: Screenjelly