This is one for thoes you you who wont to learn about web app security. It's a very nice downloadable site to teach about web application security. And it's FREE!

webgoat by

The WebGoat project was created to help everyone learn about web application security problems in a safe and legal environment. This project has created an application that will serve as;

An Interactive Learning Environment for Web Application Security

A Testing Platform & Benchmark for Security Tools

Why the name WebGoat? Developers should not feel bad about not knowing security -- even the best programmers make security errors. What they need is a scapegoat -- get it? Just blame it on the Goat!
it can be found at

it's well worth the download! Have fun