ok, well, i've been meaning to do this for a long time so here goes...
del.icio.us is basically a site for storing your bookmarks online... for anyone who uses more than one computer, that kind of service is invaluable - if you use multiple computers i'm sure you've encountered the scenario where you're looking for something you bookmarked only to realize you bookmarked it on a different computer... things you bookmark at home aren't going to be much use to you at work and vice versa...
but wait, there's more... even if you only use one computer del.icio.us still has benefits... let's say you found a page you want to bookmark but it would fit equally well into multiple folders in your bookmarks/favourites - what do you do? you're only real options are to choose one and hope you look in the right folder the next time you're looking for it or create multiple bookmarks in each folder... del.icio.us recognizes that pages can fall under multiple categories and instead of giving you folders to put them it, it lets you tag your bookmarks (very much like gmail giving you the option of labelling your emails instead of putting those in folders)...
oh, but wait, there's still more... you can see other people's bookmarks... i know what you're thinking, yes that means other people can see your bookmarks and maybe there's something you don't want other people to see... well, as yet there are no private bookmarks in del.icio.us but it's my understanding that that's going to change real soon, and besides which it's been my experience that most of my bookmarks don't really need to be private (those that are i simply don't enter into del.icio.us yet)... the benefit of being able to see other people's bookmarks is that you can find people who have similar interests to your own - say for example if you had a bunch of bookmarks tagged "cooking" you could look at the "cooking" tag and see all the bookmarks that anyone has tagged "cooking" because maybe someone else with the same interest has found something that you hadn't found yet...
on top of that, if you wanted cookbook recommendations, you could go to the cookbook tag's page and look at all the links that people had tagged cookbook and look at the number of people that tagged each link... you see, making a bookmark indicates that one finds the page interesting enough to return later - the more people who bookmark the same site, the more people who found it interesting and the more relevant it's probably going to be to you...
personally, i just like the tagging... i find it a much more natural way to categorize things so it's much easier for me to find things later... in fact, i like it so much that i've made del.icio.us my home page - specifically, i've made the page showing all the bookmarks i've tagged daily my homepage because it shows all the things i use daily... it's really allowed me to become much more organized about the way i use the internet and i think has helped make me more productive...
