Among the crop of new interconnected web2.0-ey sites, here are a few that I find very useful
BackType tracks your comments across numerous blogs. It’s on sidebar #2 (Commentosphere) and I really like it. (cocomment & commentful are good ways to report the whole discussion, but I want to just show MY comments)
Delicious stores and indexes links that you choose, and allows a few sentences. It can post a daily digest to your blog (but that function seems to be going haywire at the moment!)
Friendfeed is probably the most well-known of the new ‘lifestreaming’ services; feed it your ‘favourites’ from various sites (youtube, delicious, RSS) and it will collate them into a stream of your online activity (see ‘Cool Stuff’ in the far sidebar)
Yahoo Pipes are a collection of online apps that do very specific things — like unix, when used in conjuction (piped) they be quite powerful. I use a yahoo pipe for feeding my amazon wishlist into friendfeed.