Loopt shows you a map, and your position on it, and also the positions of your mobile friends who are in the vicinity. Now you need something to do--somewhere to get together. Loopt detects businesses in the area and makes suggestions based on your interests or specific queries ("beer, pizza, bowling"). You can read what any of your friends have said about prospective meeting places, or read reviews from Yelp to help you decide.

When you've found an agreeable destination, you can then invite your friends, and access directions for getting there, as can your friends. You can also search out new friends by looking for other Loopt users who have similar interests (favorite bars, say) to yours. (http://www.loopt.com/)

Blip.fm

I'm not the first to make this comparison, but Blip.fm really is like Twitter for music. What you see at the site is a scrolling list of people's song choices with their short comments about them. These are called Blips. You can listen to the "blipped" songs as they come up, or skip up and down the list to songs you like. If you like a particular user (called DJs here), you can give them "props" for the songs they play, or you can choose to "follow" that DJ. After you have found a decent number of DJs to follow, you can switch to a mode where you see only that group's blips.

If you think of a song you want to blip, you just search for it (you can find almost anything), make your selection from the search results, write a little comment about it, hit send, and then your blip is added to the stream of other blips. The site then shows you the other members who have also blipped that artist. It's surprisingly engaging and fun, especially if you find good DJs to follow, or if your own real-world friends sign up and participate. (http://www.blip.fm/)

Power.com

There aren't many sites with 5 million users that we haven't heard of, but Power.com is just that, and it's a name you might be hearing a lot more of this year. The "social inter-networking" site, as the company calls it, operates on the premise that many of us now belong to several social networking sites and that it's a hassle to log into and post to each one separately.

Power.com lets you log in once, then view (and post to) any of a long list of social networking sites that you sync the service up with--all from one place. You can see the posts, status changes, and so on, of your friends on multiple social networks, and simultaneously send new messages or updates to all of those sites (similar to Ping.fm). You can also automatically log into, and instant message using MSN from within Power.com--cool.