If you are like me and use the Mozilla/Firefox LiveHTTPHeaders extension all the time, but are unlike me and instead want to do the same thing in Internet Explorer all the time, or maybe you’re like me and want to figure out just why the hell IE is behaving like it is, you will be pleased to know that there is Fiddler. Here’s the MSDN page on Fiddler.

OWASP‘s WebScarab is another useful HTTP Proxy.