Livejournal and Jabber
I've always been a fan of livejournal's approach to websites, and one of their products, memcache, makes such a difference to the speed of my employers website it's unreal. As a result, I'm always keeping an eye on what they're up to. The blogosphere has a small buzz about livejournal integrating Jabber onto their site. This adds an even larger jabber-able pool of people to the vast amount added by Google when they launched GTalk. I epecially like the buddy integration - it provides a very nice way of adding interactivity to a broadcast medium like blogging.
I'll be watching this one closely - you may even see something similar on one of the sites I work on soon...