I came across del.icio.us in a rather oblique way because one of the Mozilla Firefox extensions has a toolbar for it. It's a bookmarks manager website with the additional feature that all bookmarks are shared so you can see what everyone else has bookmarked and also who else has bookmarked the same websites as you have. The main page, with its neverending parade of useful and sometimes bizarre links, is also rather interesting and great for finding blog fodder.
I'll be going to the In Honor of Floopy's 3000th Find Cache in Oak Ridge this coming evening. I guess it would be silly if I didn't go considering that it's for me. :)