The first real application I wrote using appengine, this was the reason I learnt to use appengine.
The metaserver takes requests from games, and lists them. It can act as a server list for games
To list servers go to "http://placeholdermetaserver.appspot.com/list?" and append the name of the game (or /list?*) for all games.
To submit a new server, append "/submit?(Server name),(IP address),(Game name),(port),(tag)" the important thing to note here is the returned string, the sixth value returned in angled brackets is a code, this code is used to remove servers.
To remove a server append "/remove?" and the key that was returned when the server was created. Servers will automatically be removed after 12 hours.
A repository of various bits of programming I have released
Some stuff is open source, some is closed. If something is closed that you want opened, try emailing me and I'll consider it