Affiliate Marketing, a subset of SEO, has always been a tricky business. Thankfully, Mr. Ploppy has kindly put together a list of some of the best Affiliate Marketing tools around. So, if you're in the SEO business, or have ever wanted to find out more, give it a look. Be forewarned though that there are probably as many black-hat tools there as there are white-hat. A good list, nevertheless.
(What is Affiliate Marketing?)