Social bookmarking - what do you use?

I’ve just started using a rather cool little plugin called Social Bookmark Links, which automatically generates links to all the top social bookmarking and news sites. You can see what it looks like at the bottom of this post.

There’s two great things about a plugin like this - the first is that it lets your readers easily bookmark a page they found particularly useful. But it also means that it’s the readers themselves that end up promoting your content. That gives you more time to write compelling content that they’ll want to bookmark or share in the first place.

My problem at the moment is deciding which sites to include links for. The plugin I’m using has 70 predefined sites (most of which I’ve never heard of).

So I thought I’d ask you guys. What social bookmarking sites do you use? And do you use them for keeping track of interesting sites, or are you actively marketing your own content?