I recently got a del.icio.us account and am quite happily moved in. Why should you? Because tags are so much better than folders for organizing bookmarks, and you should be able to get to them from anywhere. If you feel a bit uneasy trusting a web site to remember your bookmarks you can regularly export them (with your username and password).
I’ve known about RSS for awhile, but never really appreciated its utility until seeing Kathleen’s friends page. This LiveJournal feature is basically a news aggregator, gathering recent posts from all her friends and putting them all in one page in her layout. It’s a great idea, but there’s no reason you can’t use another feed reader since every LJ blog is automatically syndicated. Bloglines is the web-based news reader I’m using lately so you can see what I might be reading lately. (Bloglines also has an export)
I like this direction of the web. Move everything to web servers, give users bookmarklets to make interacting with everything easy. As you can now get great browsers for any OS, the web is becoming the new desktop. Of course this fear of platform independence is what drove Microsoft t0 commit antitrust back in the nineties, when Netscape and Java (multiplatform) were starting to take off.