Basically
http://btcclicks.com is a PTC variant that runs solely on bitcoins. Members pay to advertise on the website and then earn bitcoins to click ads and to refer other members who also click ads.
The website is currently in development but is expected to launch soon. There's a subscription form on the website so you can be notified once we launch.
Advertisers can also benefit from receiving highly targeted bitcoin-niche traffic for a low as 0.1 BTC/1000 visitors.