HTMLSpy is a simple source code viewer that can be used to view the source code of any web page in a color coded, neatly formatted editor window.
It works similar to the existing View Source option but adds an additional entry to the IE right click menu (HTML Spy), which launches the source of the page and can also mark selected section, so that a specific code snippet can be easily located.
You can also modify the source code and preview the results in your browser, without having to save the page first.
30 day free trial for Windows 95/98/Me/NT/2000/XP, supports MS IE 4.0 or higher.