I used the freeware tool Locator to update the locate database (which contains all the files on your system). Next I searched with Locator for index.html.
If you select to search starting from / (i.e. root), you'll get a massive list of index.html files, most from the /Developer directory (if you installed the developer tools). Scroll down in the results to the bottom where you'll find the Unix tools in the /usr directory. Select the page you're interested in and click on 'Open' in the toolbar. The page will open in your browser where you can bookmark it for easy access.
Pages I've found on my system included html documentation for TeX, LaTeX, ImageMagick, Postgres, GhostScript and even the O'Reilly book "Using Samba, 1st ed." Those who are into the X11 and Fink stuff will probably find many more.
[robg adds: In testing this, I found I only had a couple of index.html pages in my /usr directory. But I did, indeed, have a ton of pages in fink's /sw directory. You'll save a lot of scrolling in the results if you start the search directly in /usr or /sw (or /Developer) as opposed to the top level of the drive...]

