Social bookmarking sites allow you to save your favorite websites, to tag them, create lists, and to share them with others.

Try these:

Diigo Create an account, and download the free toolbar buttons that allow you to bookmark, highlight, capture, read later, add filters, and more.

Here's a tutorial on how to use Diigo (you need to override the filter and then refresh this page in order to view it at school):

Delicious All of your bookmarks, all in one place. Similar to Diigo.

Traditional Online Bookmarking Web Sites
As you discover interesting Web pages, use the Backflip it! button that you save to your toolbar to save them. Backflip will then organize them for you in your personal directory &endash; which you can access from any computer. You add a button to your links bar to ”backflip” any site to your favorites.
ikeepbookmarks* allows you to upload, and keep, your bookmarks on the web for free. You can access them from any computer. Allows you to import your Internet Explorer Favorites or Netscape Bookmarks. Easily share your favorite pages with friends and associates.
Your personal bookmarks and other information are kept secure, password-protected, and available only to you. You can use one of the ”MURL Gadgets” to upload bookmarks from a number of sources and download them to a number of destinations. A window will stay in the background as you surf the Internet allowing you instant access to MURL storage.
Use an easy URL for your bookmarks ( Create and then fill categories by adding bookmarks to your favorite websites (also as many as you like). Uses a small pop-up window that you can use to paste in the title, URL, and description. Keep the window open as you browse the Internet.
Yahoo! Bookmarks*
Yahoo! Bookmarks allow you to store links to your favorite Web sites on Yahoo! and access them from any Internet-connected computer. In addition, you can store your Yahoo! Bookmarks in folders to better organize your favorite sites. As an option, you can use Yahoo! Companion (*), a browser toolbar, to quickly add to or access your Yahoo! Bookmarks from a drop-down menu in your browser.