Diigo is a browser toolbar that makes it easy to comment on pages, save sticky notes and highlight text, as well as create a simple bookmark. The toolbar is available for Firefox and IE, though there is a lighter bookmarklet for other browsers.
When you use the Diigo toolbar, you enter comments and other text into a browser interface (a pop-up bookmark form, or the Diigo sidebar). The process of “annotating” a page feels fast, because most of the work happens in your browser.
Everything you enter is stored on Diigo’s servers. Everything you enter is available to other Diigo users, unless you choose to make it private, or only available to friends. That annotations are public means that Diigo is a good research tool, even without people you know using it. The Diigo public groups feature is a way to find topics that are of interest to you.
Where I Diigo would be most useful is with a group of people researching together (or friends who enjoy sharing sarcastic comments line by line, like a textual Mystery Science Theater for the web). Though I cannot imagine giving up the horizontal space of browsing with the toolbar open, giving it a try does change the browsing experience. Diigo does not require you to keep the toolbar open, but doing so lets you discover other Diigo users’ takes on the current site you’re viewing. For example, I learned that comments about YouTube are only slightly better than YouTube comments themselves.
I have some issues with the Diigo defaults. The toolbar takes up most of an entire horizontal bar in Firefox, with a dozen buttons when it installs. Saving a page is split amongst four of those buttons, including individual interfaces for bookmarking, highlighting, and commenting. Also, be sure to check your Diigo settings. There are seven different email choices, most of which default to send you messages.
Though I’m impressed with the speed and usefulness of Diigo as a toolbar, I might choose the lighter bookmarklet over the feature-heavy version. It can be used in many of the same ways, but only activates when I ask it to.
[Diagram courtesy of Diigo]