ifttt - Stands for If This Then That. You know how most online services have alert functions now? For instance, if you receive a message on Facebook you can have it email you or send a text to your phone. Well ifttt is that kind of service but you can apply it to anything. You can have it call you every time one of your friends checks into the bar down the street on foursquare. It ties into an impressive number of services, including: Craigslist, facebook, Flickr, foursquare, most Google services, Instagram, LinkedIn, Twitter, Youtube and more. It's already been immensely helpful in setting job search alerts on Craigslist. I highly recommend.
gdgt - A show-off-my-collection site for electronics. Create lists of things you own or want to own, from the past, present and future. Compare lists with others, comment and ask questions. It's also an interesting place to get new updates about the latest interesting technology coming out.
Weotta - A social planning site, useful in finding an itinerary for an unplanned weekend night. You enter what kind of crowd you're running with, what mood you're in, and Weotta will give you a list of things to do. For example, one plan is to grab dinner at a new cajun restaurant, go see the Deftones in concert, and then drinks at a hip, bayside bar. They only have San Francisco and New York so far but I'm really excited to see what they do with the service.