Currently I have a new script which is basically a link selling script. However it is fully automated, so that when someone buys a link and pays for it they link is instantly activated and live on the site. Its like having your own ad-bright / adsense on your site. Also you can install the script once and run the code on multiple site, which allows you to create a multi point hard links on multiple sites instantly. Prices, maximum links, link title length, customers, and everything is controlled with a easy to use admin panel.
The best part is its free, and if you want to see a live demo just checkout the top left hand corner of
http://www.dailybabesblog.info
The only down side to this is that it only accepts paypal right now. However if you have a different payment processor that you would like to use then I would be more than happy to integrate it.
The script requires Zend Optimizer which is on many hosts, also it is PHP with a MySQL database so it should work on almost anyone's hosting.
If you saw the live version on my site, like how it works and wouldn't mind using it for you site. Then let me know and I will give you a free copy.