Google Celestial Sphere
First came Google Moon, Then, this week, Mars and Europa, not to be confused with Europe ;-)
But I think that the big one is not yet with us, Google Celestial Sphere
The skies by night, northern and southern hemisphere, stars and costellations... It can be managed with lat/lon and image tiles, just as Google Maps.
And when the API is created for that... We'll have Tagzania Space! I think that it may make sense, to have personal/social bookmarks and tags over the skies. So much amateur astronomy and instituions out there, all very much conected to the web. A new extra-solar planet here, a supernova there, predicted position of comet X for tomorrow night, Star Trek interest points... Much more to tag in the universe than in Mars alone.
Ilustration below, the one and only (as far as I know) Basque placename in Mars, Galdakao:
