The other about links that fall into the useful category are about:cache which displays cache statistics and the location of the hard disk cache. It provides links to display the contents of the files that are currently cached in memory and on the disk. The other protocol link that can be useful on some occasions is the about:plugins protocol link which displays all plugins that are used by Firefox. I have written an article that is explaining how to make use of that link to check and remove plugins in Firefox.

All other Firefox about links are not that useful in my opinion, below is a list that lists all known ones:

• about:
• about:blank
• about:bloat
• about:buildconfig
• about:cache
• about:config
• about:crashes (only Firefox 3)
• about:credits
• about:logo
• about kitchensink
• about:license
• about:mozilla
• about:plugins
• about:robots
• about:support

Just type the links in the location bar if you are curious about their purpose.