So imeem demo'd at Demo. imeem is a windows application that brings together social networking, im, filesharing, picture sharing and blogging in a single, caching windows application. It's really cool technology and they have a solid design sense, which is something I really like a about them.
One thing that I think they are doing especially right is that all communications are cryptographically secured. This is a very right way to do IM. It is invitation only, but if you are interested, I have some. Please note I'm an advisor to the company, but that's not a bad thing :-)