Kontera.com - get paid for content link turns relevant keyword

Kontera - With Kontera you insert javascript code into your blog or site's HTML and Kontera then crawls/examines your site's content. Kontera will then turn certain words within your blog or site posts into clickable ad links. Should the links be clicked by visitors, you earn money for the clicks.

(+) Able to be run with Adsense as a secondary income source (as long as you differentiate the two a bit). Very easy to integrate the Kontera code into your blog/site's code.

(-) Getting accepted by them might take some time (until your blog's getting the traffic & rank they want). You also have to make sure the code doesn't turn your blog titles and headlines into ads, making things look strange. Click earnings are on the lower side. With a minimum $100 payout required, it can take a while to see a payment from Kontera. However, it remains a popular additional money maker to this day for many sites.