If you are interested in having your own contextual ads that make a link out of certain keywords, take a look at what http://www.AfterSense.com is offering. I just paid for a copy and will post more once I start using it, but it allows you to set up certain keywords and then make links out of them on your site. You add JavaScript to the pages, and then the server takes care of making the links. It's good for sites with lots of content, like an article site, and where you might have affiliate programs where the links need to be changed easily on a entire site.
When you mouse over a link, it pops open a small window with more information and then you can click on the link there. You have to do a lot of set up by hand, but the nice thing is that you have the control. They have an affiliate program, but the above link is not an affiliate link.
When you mouse over a link, it pops open a small window with more information and then you can click on the link there. You have to do a lot of set up by hand, but the nice thing is that you have the control. They have an affiliate program, but the above link is not an affiliate link.