Fiddler - an HTTP traffic logging utility

Fiddler is an HTTP debugging tool. Fiddler acts as a local proxy and then logs HTTP traffic between your computer and your intranet, and the Internet. Fiddler allows you to inspect TTP Traffic, set breakpoints, and in a sense "fiddle" with incoming or outgoing data (hence the name). Fiddler is simpler than Netmon, but it acts only on HTTP traffic. While you see none of the lower layers, the view at the HTTP level is good. Fiddler also looks extensible, with scripting, custom inspectors, and menu extensibility. And: it's free!