I'm really starting to like Del.icio.us which advertises itself as a social bookmarking site. The idea is simple, you click on a bookmarklet anytime you want to bookmark a page, up pops a Web page with the page's title and description. You can edit those field and enter an extended description or comment and free-form keywords. Each of those keywords becomes its own bookmark list, complete with RSS feed.
I've been using it exclusively instead of traditional bookmarks because I like its flexibility. I can store something easily and in more than one place. I can create custom bookmark lists for other people to read. For example, I've started a bookmark list for my class and they can follow it in their feedreader. The fact that I can add my own comments also makes it usable as a linkblog of sorts and its more flexible and easier to use than most blogging software for that purpose.
Another think I'm doing with Del.icio.us is just using it to hold stuff I want to read later or know I'll want to find. Because I can put things in multiple categories, I can easily create my own categorization scheme.
Del.icio.us lets you look at other people's bookmark lists too and even aggregate them. For example, I've classified some pages as having to do with messaging. I can also messaging for all users and see what other's have classified under that tag. I haven't found that to be as compelling, but I think with a little coordination, you could get a group of people sharing keywords and build some powerful bookmark lists.