I'm a huge fan of the Live HTTP Headers plug-in for Firefox. It can be a lifesaver when it comes to debugging complicated redirects and cookie issues. Well today I was doing some debugging in IE and I wanted to see what headers were being passed to and from the server. A little looking and I found ieHTTPHeaders. The tool doesn't have all the features of Live HTTP Headers, but it lets you see request and response headers from a window in IE which is all I needed.