Here are all of the useful (and not so useful, but still funny) about: triggers you can type into your address bar.
about: — The same page as “Help -> About”.
about:blank — A blank page. Useful for setting as your homepage.
about:cache — Displays cache statistics and disk cache directory location.
about:config — GUI for modifying user preferences.
about:crashes — List of Breakpad crash reports, with links and datestamps. Only in products based on Gecko 1.9 or later (Firefox 3, Thunderbird 3, SeaMonkey 2).
about:credits — The list of contributors to the Mozilla projects.
about:logo — Displays the application logo (Mozilla Suite, SeaMonkey, and Firefox 3).
about:kitchensink — Was never included in Mozilla for the reasons listed in Bug 122411 (“Mozilla does not have a kitchen sink”). You can install an extension that adds it though :)
about:license — shows the Mozilla Public License and the Netscape Public License for the piece of software. ( Only in products based on Gecko 1.8 or later)
about:mozilla — The famous Book of Mozilla.
about:plugins — Lists all your plugins as well as other useful information.
about:robots — Easter egg, see bug 417302. Beginning with March 8th, 2008 trunk builds, it’s now available on Firefox 3.0b5.
List is courtesy of Mozillazine. From the useful to the silly, which of these is your favorite?
