Today I found a really nice web application security presentation by Joe Walker.  Honestly, almost none of it is common sense and I would therefore encourage all web developers to check this out.  Also on the same page as the presentation are a number of very good AJAX security links like the XSS (Cross Site Scripting) cheat sheet.

BTW, this type of stuff is touched on in the Brainbench AJAX exam.

Links

• Web Application Security Presentation by Joe Walker