Daz3d is a site that has to do with 3d designing. They have their own program call DazStudio which lets you do a lot with Poser characters. For a time this program was available for free.
If you become a member (membership is free) you can also apply to be one of their affiliates. Once you have been approved you can paste the affiliate codes onto your site. However unlike the adsense program you have to make $100 during the quarter (not monthly like adsense) before you can have your payment paid to you via Paypal. You also have the option to use the earnings for "store credit" in order to buy things at Daz's website.
So if you're into 3d designing this would be a good opportunity for you to get some added income.
By the way, you can see my 3 designs by clicking here. I'm not ready for my first animated short but I have come a long way from Poser 1!