Go hack yourself, with .NET Rocks episode 914, Hacking your website with Troy Hunt.
This discussion goes into how you can test the security on your own website. We all know about things like SQL injection but Troy give a lot of great advice on other points of security.
Did you know that someone can put your site in a frame and then on top of that for example a form. It looks like you’re filling out the form on the regular site but instead you’re filling it out on the hacker’s.
Always good to hear things about security to be reminded. I think a lot of developer’s, me included, fail on this point sometimes.