There are two things going on right now that really capture my attention (as far as web 2.0 goes):
I talked about Twitter before (here and here). I did not mention facebook much I think. I became a member a month or two ago and have been loving it ever since. Not only is it the best and cleanest social networking site that I've come across, the recent additions of applications into facebook is very interesting. It is possible for third-party developers to build application inside facebook. There are now a couple of hundred of those, most interesting web apps also run in facebook now, such as last.fm, the zoho apps, google reader and many more. Here's my public facebook page (it only shows very little information).
Facebook is aiming at becoming an operating system, which I find fascinating. People have been trying to build Web OSs for years but none really succeeded, will facebook succeed? They just might I think. If you don't use facebook yet, I suggest you give it a shot.