Zootool is a free, fun and easy to use, visual bookmarking service I found out about from my PLN on Twitter this past week.
Zootool allows you to bookmark, organize, and share your favorite web links, images, videos and documents easily. You simply install the browser extension (Firefox, Chrome, and Safari) and then start bookmarking. You organize your bookmarks in "stacks" and can add tags for easy organization and searching later. Your bookmarks are visual on in your Zootool page. You can also share your bookmarks via email, Facebook, Twitter, or Tumblr. There is also an iPhone app and a mobile optimized version for Android.
You can even import bookmarks from Delicious, Pinboard, Google Chrome, Safari, Firefox or many other services and browsers. Videos, bookmarks, images and documents can all be viewed in your Zootool collection.
This is a great tool for educators and students to use. They can bookmark resources for projects and for class and then share with others easily. It's another great resource for collecting and sharing online resources.
Google for Education Resources (including bookmarking and bookmarklets)