i89.us - Export to several formats, see popular & recent bookmarks, ability to shorten URLs.
AllMyFavorites.net - Create an organized page for your bookmarks that you can share with friends and family, access from any computer.
Backflip.com - Check out the most popular links each day, set "The Daily Routine" as your homepage so you can visit your must stop sites each day with ease.
BibSonomy.com - Public & private bookmarks, tag cloud, related tags, duplicate detection with the chance to merge their info.
BlinkPro.com - Dynamic folders, bookmark all links of a page plus all the usual features.
BlogMarks.net - Save your bookmarks, tag them with keywords for easy searching amongst your list, share with others.
Bluedot.us - Tabbed user page showing a network of friends, bookmarks, and related tags. It allows you to import contacts from all the major mail services such as GMail and Yahoo.
BmAccess.net - Bookmark a site, add tags, when you look up a tag, you get the names and a little thumbnail image of the site along with it.
BuddyMarks.com - Store your bookmarks online, share some or all of them, discover new sites to visit by searching the public bookmark area.
Chipmark.com - Browse random "chipmarks", share them, sort, filter, and get personal recommendations.
Complore - 10MB of file storage, public & private sharing, tag cloud, popular feeds and more.
Connectbeam.com - A themed social bookmarking site for enterprise-scale business.
Connectedy - Import your bookmarks, batch edit them, check in on hot topics.
Connotea.org - A themed social bookmarking site specifically for researchers, clinicians and scientists.
Diigo.com - Highlight portions of a page; write on it like you would a piece of paper, share with your group, and search all publicly saved pages.
Excites.com - Organize your bookmarks by tags, add comments and notes, share publicly, subscribe to certain tags so you can be notified when a new site is added that may interest you.
Feedmelinks.com - All the usual social bookmarking goodies, but you can also add links via email.
GetBoo.com - Export your folders to HTML, import and remove duplicates, delete all bookmarks.
Givealink.org - Donate your bookmarks to this site to help them recommend sites and get a better understanding of how each person bookmarks.
Hyperlinkomatic.com - Import/export, categories, notes, sharing, block users, RSS, tags.
IKeepBookmarks.com - Folders, search folder names and more.
Lilisto.com - Ratings, notes, categories, smart categories and in-page editing.
Linkroll.com - Links open in new window, subscribe to tags, browse by archives.
Ma.gnolia.com - Discuss all the saved bookmarks in groups, see what the Featured Linker is all about, join discussions in the Hot Group.
Mister-Wong.com - Bookmark and tag, search for tags that interest you, make buddies with people who have interesting saved sites.
Netvouz.com - Save your bookmarks in folders, tag them with keywords, share them with others or password protect them.
Nextaris.com - Folders, tags, clippings; store up to 100MB for free.
Shadows.com - Share your already existing bookmarks, discuss and rate sites and see what you can find.
SocialBookmarking.org - User and global tag cloud, blogs, social networking, avatars and more.
StumbleUpon.com - Lets you "channel surf" the Internet and review sites; it learns what you like and recommends more of the same.
Unalog.com - A basic social bookmarking site, but with the ability to look back at specific days and see what was going on.
WireFan.com - You can vote on links as well as add thumbnails for sites.
Xilinus.com - Tags, rating, search, public & private listing, drag-and-drop sorting.
Yahoo! My Web - One button click adds your bookmarks to the search engine giants system features duplicate detection to help you keep your bookmarks tidy.
Social Bookmarking Sites with Clipping
BlinkList.com - Save sites for later reading, share your list or keep it private, even send your saved pages to your blog for wider sharing.
Clipclip.org - Like an online scrapbook, you clip out the part of the site you want, then share it with whomever you want, and discover new places to visit.
Clipmarks.com - Allows you to clip just the chosen bits of a webpage, save them to the main website, or even insert them into your own blog. Think of it as fancy block quoting.
del.icio.us - You add your bookmarks and access them from anywhere. Check out what others are saving and see where it takes you.
Furl.net - Not only can you do the standard bookmarking and sharing, you can save archived versions of a webpage and even export all your saved pages to a ZIP file.
Linktopia.com - Keep private, share, mark as friends only, edit bookmark dates.
RawSugar.com - Can cluster your tags for you based on recommendations by other users.
Simpy.com - This social bookmarker does all the usual plus detects links that have changed, and distributes your bookmarks via your blog's RSS if you like.
Spurl.net - You can upload your existing bookmarks to get started, add more for centralized access, and check out hot lists and recommendations.
SyncOne.net - All the usual features plus the ability to add your own Google Ads to the top of your profile page.
URLex.info - Inbox, group creation, directory, all of the usual features, plus being able to send your RSS feed to the site.
Blog-buzz.com – It is similar to Digg, but for blog posts.
Digg.com - Synonymous with social bookmarking: you Digg a story, others Digg it, the more popular it gets the better chance it has of hitting the first page.
Netscape.com - A former contender in the browser wars, and the "mother" of Mozilla, it's now a a social news aggregator with voting of stories similar to Digg.
Newsvine.com - Users can write articles on current news events, save links to external content; vote, comment and chat on article pages created by both users and by journalists.
Reddit.com - You vote up or down on a story making it move around on the home page.
Shoutwire.com - Similar to Digg, except instead of "Digging a story", you "shout it". Still a way to vote on unique Internet news stories.
Thoof.com - Add news stories you find interesting, anyone can "improve" the article by fixing the URL, editing the summary and more.
If we have missed any website then you can add more sites in the comments.