I am a little late to the scene with this one, but to be honest, I had no idea what del.icio.us was. I did not understand the premise of the service, and I did not (at first) see what benefits it offered.
I must have been blind.
del.icio.us is a social bookmarking community. Buzzwords aside, del.icio.us lets one post bookmarks to a web page that anyone can access. The site keeps track of how many people bookmark a certain site and how popular sites are based on how many recent bookmarkings particular sites have had.
The feature that really makes investing is del.icio.us worthwhile is tagging. One may add as many tags to a link as he wants. For instance, if I bookmarked this site I would tag it with “blog” and perhaps even “apple.” Since I started using the service last week, I have about one hundred bookmarks and hundreds more tags.
del.icio.us can be used for countless different things, most of which make your life a lot easier.