There's yet another new bookmarking utility live now: Diigo. This one is different. In addition to letting you bookmark pages and share those bookmarks with others, it also lets you highlight parts of pages (text or images), and store those highlights not only in your Diigo account, but also on the Web pages themselves (if you have the plug-in). You can also attach Post-it-like notes to your highlights on Web pages, and they can be private or shared.
Old-timers may recollect one of the first Web annotation services, ThirdVoice. That tool also let you mark up any Web page you visited so that other ThirdVoice users could see what everybody had to say. The service died in a firestorm of controversy, but we've evolved since then--what people used to call "graffiti" we now call "interactivity" and "community."
The annotation capability sets Diigo apart from Del.icio.us and makes it a more granular data-gathering tool, like ClipMarks. Diigo lets you take your clips and do useful things with them: you can publish them all as a Web page or directly to a blog, or you can send them in e-mails.
With the Diigo toolbar installed, you can also easily mark parts of any Web page and forward this directly via e-mail. It's a handy and universal "send this article" function, and the highlighting tool makes it much easier to add context.
It took me a while to grok Diigo, though. There's a lot going on here, and like a Swiss Army Knife, there are blades that new users will find confusing. What's a customizable search bar doing here? And why does Diigo act so much like a social bookmarking tool--do we really need another one of these? Diigo has very useful annotation and organizational features, though, and if you want a good way to mark up the Web for personal use or a fast way to send clips to people you know, it's worth checking out. See also Jeteye.
There's also a nice review of Diigo on Solution Watch.