The biggest Social Bookmarking sites are Digg, Reddit, StumbleUpon, and Del.icio.us. I use the term a little loosely, as Digg, Reddit, and StumbleUpon are generally referred to as “Social Media” sites, as they’re less about storing things for later reference, but about finding things. If I’m collectively talking about the four sites, though, I use the term Social Bookmarking. After all, you still are bookmarking with the sites, even if that’s not the main focus.

The Social Bookmarking sites are all a bit different, and they all have their own uses.

Digg/Reddit: Digg and Reddit are mainly for finding “news” (which is a broad term on the two sites). Using the sites, you can find things that a large group of people think are interesting/useful/relevant/etc. Looking for the hottest tech news? Head to Digg.

StumbleUpon: SU is channel-surfing for the web. Just click the “Stumble” button on the SU toolbar and you’re taken to a semi-random page in your selection of interests. Do you like the page? Click the “Thumbs-Up” button. Your vote affects how often the page will come-up when other people click their Stumble buttons. It’s fun, and addictive.

Del.icio.us: Wouldn’t it be great if you could access your bookmarks from any computer? Wouldn’t it be useful to see what other users (people you know, people with similar interests) have bookmarked? That’s the idea behind Del.icio.us. You import your bookmarks from your browser (most major ones supported), and then you start bookmarking things with the Del.icio.us instead of your “normal” bookmarks system. If you don’t get why you’d want this, watch this short video.

All of the aforementioned sites are useful, and you should check them out if you haven’t already. In the blogging world, they are useful for finding things to write about, and for promoting things you wrote. Don’t blog in a vacuum.