I like the concept behind Flagr.
Flagr is a site that lets you tag areas of a map. You could walk out of a restaurant you really liked and with your cell phone tag the location of the restaurant and write “Great burritos here!” Or you could tag a good hiking trail like that, tag landmarks for your visiting friends to visit. Of course, you can also use your computer to tag things too, but I like the idea of being able to do it immediately after you’ve visited the location.
You could use something like Google Earth to do the same, but you wouldn’t be letting other people know about the great burritos.
Not a lot in my area though.