Bumpzee is a site I just found out about from the wonderful professional guru, Kimberly Wright. Bumpzee is a site that is very similar to Skloog and SpeedyMarks that allows people to share their and organize bookmarks in a visual way. However, I'm not sure how appropriate this site would be for students due to some of the content, but it should be ok for teachers to use among themselves.
For looking for a better educational solution I would suggest Diigo for social bookmarking.
Click here to give Bumpzee a try.