The catch is that the traffic isn't always buying or clicking traffic, but it can be traffic that build backlinks to your site. It can be quite valuable.

The beauty of being well ranked in social bookmarks is that it means people have found that page of your site interesting in one way or another. Maybe it's useful information. Maybe you made them laugh. Maybe they think it's so bad the world needs to laugh at you. But in any case, you're getting attention to your site.

But there's a big catch. Many sites frown on your promoting your own websites. You can't be too obvious about doing such things if you really want to succeed.

You also need to be a part of the community. If you make a lot of friends or join groups on the social bookmarking sites you consider to be important, you have a better chance of your sites getting more attention. Just bookmarking your own site doesn't do much good unless other people do it too.

To get attention you have to pay attention. Bookmark other sites. Participate. Just as in marketing on forums and blogs, the more you participate the more you are likely to get from your efforts.

When you bookmark a webpage, you generally need to tag it or otherwise categorize it. The tags will help it be found. In fact, as you post to your blog it is a good idea to include Technorati tags so that your posts are easily found there.

But Technorati doesn't often send all that much traffic. Digg, on the other hand, can send server-crashing levels of traffic. StumbleUpon can do well too.

When you promote your site too much, you run the risk of being labeled as spam by other users. You have to be very careful about how you promote, or risk losing your account. This makes doing plenty of honest bookmarking of other great sites very important. Combine this with only bookmarking your own sites when you have something you think is really unusual and valuable.

Another way to increase your odds of being socially bookmarked is to provide links for it on every page of your site. People bookmark pages, not just sites. For WordPress users there are plugins to make this very easy. You can also add a link from OnlyWire that will handle this for you on any page. The basic code they give you requires that you enter the URL and tags you want used, but it's a way to get things moving. Users have to sign in with the service, which can be something of a disadvantage.

Not every submission you make to social bookmarking sites is going to do anything with you. Many will just fall through the cracks. But when it works out the results are amazing.