What are social bookmarking sites? Basically, these are sites that allow users to post their favorite sites, using tags (or keywords) to categorize and organize them, then other users can take these bookmarks and add them to their own collection or share them with even more users. Here are top 10 social bookmarking sites on the Web - the sites that consistently deliver some of the best content you'll want to share, discover, and store.

1. del.icio.us

del.icio.us is a social bookmarking site that has rapidly taken off even more in popularity since being purchased by Yahoo. I use del.icio.us probably the most out of all these top picks, particularly to post interesting sites that I've found around the Web. I also subscribe to quite a few del.icio.us tags, such as popular and reference, and I get all the sites tagged with these keywords in my RSS reader of choice, Bloglines.

2. Digg.com

Digg is social bookmarking and social networking gone a little crazy due to the fact that anyone can submit a Digg (site), and then anyone can comment on those same Diggs. For me the most interesting feature of Digg has to actually be the comments on the sites and stories, since the Digg community is not shy about letting folks know how they feel about a particular Digg. Primarily focussed on geeky, technology-type items.

3. Reddit

Reddit is a social bookmarking Web site that works much like Furl and del.icio.us: you register a username and password, and then start submitting and sharing your bookmarks. Reddit is similar to del.icio.us in that users are encouraged to vote on the links and stories that they feel are deserving of being in the top dog spot: it’s kind of a popularity contest, so to speak.

4. Furl

Furl gives users the ability to save copies of any Web page, search within your own personal archive of Web pages, and share what you find. People use Furl to create their own personal shopping lists, real estate directories, job searches, student research papers, etc. This may just sound like a fancy way of saying bookmarks; but the thing about Furl is that you can access it from any computer, which means that your Favorites will go with you.

5. Clipmarks

With Clipmarks, you can clip the best parts of web pages. Whether it's a paragraph, sentence, image or video, you can capture just the pieces you want without having to bookmark the entire page.

6. StumbleUpon

The beauty of StumbleUpon, to my mind: you are able to take advantage of a vast network of dedicated Web searchers who are finding utterly brilliant sites and sharing them with you. I do have to warn you, though – StumbleUpon is an incredibly addicting way to search the Web. I found myself up till 1:30 AM one weekend, blearily clicking the Stumble! Button over and over again, because the quality of the sites are just so amazing; you just keep on coming across stuff that instantly merits a bookmark of your own.

7. Newsvine

At Newsvine, you can read stories from established media organizations like the Associated Press as well as individual contributors from all around the world. Placement of stories is determined by a multitude of factors including freshness, popularity, and reputation. Contribution is open to all, and editorial judgement is in the hands of the community.

8. Mixx

Mixx offers up an eclectic mix of all sorts of bookmarkable content; anything from videos to news to popular stories can be found here. Just pick a category and you'll be able to find lots of stuff that might merit a bookmark of your own.

9. Diigo

Diigo is one of my newest favorite Web tools. Not only can you use Diigo to save your favorite Web bookmarks, yalso ou can use Diigo to put sticky notes on websites, highlight stuff you like, comment, and more.

10. Propeller

The way Propeller works is very similar to other social bookmarking sites such as Digg or del.icio.us. Users find stories, submit them, and other Propeller users can vote and comment on those stories, with the most popular stories rising to the top.