Profilactic, which I covered previously, is now available to the public. It's a personal feed aggregator: You tell it where you post online, and it pulls all the feeds together. You can point people to this "mashup" page, or use one of the site's widgets to embed that info in your own profile page or blog.
Another social site I use, Jaiku, has a similar function--it consolidates personal feeds into one feed. Profilactic is much easier to set up, though. It has a list of sites it can read from (Twitter, Pownce, Digg, Flickr, and several more), and all you have to do is put in your public usernames for the accounts you have. You can also add a blog or RSS feed to Profilactic.
There are some hangups with this early release of the site. For one, it's a reader, not a writer: You can't post to your various sites from Profilactic. You'll have to do that from the sites themselves. And it doesn't yet read enough sites. There's no Facebook integration, for example. (A full Facebook version is in the works, I was told.) Also, the invitation system isn't yet built.
Still, it's a useful service, especially if you are a participant in several sites.
See also: Mashable's rundown of 20 social network aggregators.