So we’ve recently finished a little wordpress project: http://lockalike.com/
The idea behind the plugin is very simple – you lock your web pages and force your visitors to vote, tweet, like, share, stumble, or anything else before they can see the content. So you increase web traffic in an “organic” way. You get real people sharing your content. Not some robot script or whatever. This also means you are organically increasing your backlinks and you get your sites indexed in Google a lot quicker.
Anyway, have a look at the plugin. I’m giving my readers $10 off, so you can grab it for just $19.95 
(Couponcode = bobjones).