Diigo

Diigo is a social bookmarking site. Basically, you import your bookmarks from your browser of choice and then they are available online any time, from any computer. It is so easy. One of the best reasons to use Diigo is you can share your bookmarks with others very easily. You can also search for people's sites that they have shared. This is done by "tagging" your bookmarks by subject areas. Then, when someone is searching for math, they can see any sites you have tagged as math. Diigo also has more complex features such as using sticky notes to make annotations about the sites.
One feature @glogstereduman shared with me on twitter was to create a list, save websites to that list, then play the list as webslides. This creates a type of slide show from the websites you have saved to that list. One way I have used this was with student glogs. Here is an example of 2nd grade glogs saved as a slide show. This is truly a great feature of Diigo!