If you don’t use del.icio.us, start. Now.
OK, now you’ve started, before you get too carried away, read this article: The Several Habits of Wildly Successful del.icio.us Users » Slacker Manager.
There’s so many powerful uses for this amazing application. One I’ve just started is to track research on given topics – then it’s really simple for me to share the links with my colleagues. But becuase they’re live, and collaborative, it opens up loads of possibilities.