Clickbank is the standard choice and pretty much the market leader regarding ebooks. You should also try
http://www.paydotcom.com
If you only want to sell one ebook, you can put it up there for free. And you only pay a one-time fee of 29$ for putting unlimited ebooks up compared to the 50$ a pop you pay at Clickbank.
It's worth signing up. You get an affiliate sale once in a while even when you do absolutely nothing. But make sure you put up a sales page with paydotcom payment only for the affiliates to promote.
They use paypal, which has gotten bad rep on this board and in the adult biz, but it's quite common in mainstream and you get the advantage of getting instant payment without having to wait for checks to come. This can speed up your growth.
