Diagram tool for free

Links from Dan Bar Shalom :

Very nice online diagram tool:
http://www.diagram.ly/

Unlike all the others it is:
1. Completely free
2. You can save diagrams to images or local xml files on your disk that you can later load back
3. No registration or login needed.

Another tool that someone already posted somewhere in nation:
http://www.websequencediagrams.com/

You can create web sequence diagrams and save them as images.
You can also save the text and load it later.