DED - The Diagram Editor

This little editor lets you quickly create diagrams of all sorts, and to print them or save them as images. It's an ideal tool when you're writing informal documentation, or making a quick presentation. You can create all sorts of diagrams, including class diagrams, ER diagrams, flow diagrams, semantic diagrams and block diagrams.

Here are some examples:
Class diagram:
ER diagram:
Semantic diagram:
Here's how it looks:
Get it here: Download

The source code is also available.