Comwat is a new social networking tool that has combines a few aspects of a profile aggretator with some automatic Twitter-like functions.
This tool will let you know where your friends are online, so you can catch up with them on the particular social networking site they're currently logged into. You can also find new people on Comwat, and view their various profiles in public view or in stealth mode, in case you don't want others to know who's profiles you've visited. Comwat will also tell you the last time you viewed someone's profile, but this feature only works for public views--not stealth mode.
While you can add friends to your Comwat network, there is no way to send them a private message or leave comments (that's what the other social networks are for). The other good tool on Comwat is the ability to add other sites as bookmarks, so networking on Comwat isn't limited to social networking profiles. Including an easier way to add profiles, such as Wink's login request, would encourage users to add more profile links as well.
Other profile aggregation services include ProfileFly, 8hands, and Tabber.