YouTube is a place to discover, watch, upload and share videos.

Facebook is a social utility that connects people with friends and others who work, study and live around them. People use Facebook to keep up with fr...

foursquare

San Francisco - User Reviews and Recommendations of Top Restaurants, Shopping, Nightlife, Entertainment, Services and More at Yelp

LibraryThing catalogs your books online, easily, quickly and for free.

Flickr is almost certainly the best online photo management and sharing application in the world. Show off your favorite photos and videos to the worl...

Twitter is without a doubt the best way to share and discover what is happening right now.

Geocaching is a treasure hunting game where you use a GPS to hide and seek containers with other participants in the activity. Geocaching.com is the l...