Imo.im: The new imo.im app (which is available in beta right now) has gotten quite attractive and is a huge improvement over the current official version. The beta uses a tabbed interface (sorta similar to eBuddy) and has a brand spanking new UI where everything is a lot easier to use. The beta is only a "preview" of what's to come in the official 2.0 update but from what I'm seeing, it's pretty much ready to go. One thing: I don't like how the "Send" button is near the text box and not on the keyboard itself. Free.
Color: A new sort of social network/photo sharing app, Color shows pictures of the world around you and "friends" people by your phone's location. Color uses your phone's sensors (GPS, triangulation, accelerometer, even microphone, etc) to finds other Color users who you're in proximity to. Once found, the app will automatically add them to your "elastic network", which means you can see every picture they take from now on (whether you know them or not). It can be potentially amazing for concerts, events, and parties but is kind of confusing and awkward to use when you're just sitting at home. A little crashy on Android though.