Eyetools Research will let you resell their services and offer eyetracking studies to your clients.
For the uninformed, eyetracking studies measure where users actually look on your web site. This will include the order in which people look at things on a web page as well as where most people look (using a Heat Map). This information can be invaluable in determining how usable your web page is.
Although I don't pretend to know anything about the industry, their pricing seems reasonable and they offer discounts to resellers.
I find this really exciting and I plan to mention this to my clients (by way of this blog entry). It would be really nice if Eyetools made some materials available for use on reseller web sites and promotional materials. I would love to start offering this service in the future and have information that I could easily put on my web site to accurately and effectively describe the service.
Find out more about offering eyetracking to your clients. I will definitely continue to keep an eye on Eyetools (especially their eyetracking tests of CSS Zen Garden).