If you do and you have a reasonable affiliate program on it, I run a 7000+ subscriber strong JavaScript newsletter and would be all over this ;-) (Same goes for any good JS related products, to be honest.)
I've never run one. But the best ones I'm an affiliate on so far seem to be http://zferral.com/ and http://clickbank.com/ - they're very different. Zferral is basically a webapp that lets you create an affiliate program for your "whatever" using your existing billing system. Clickbank, on the other hand, actually hosts your product and does payment processing and affiliate stuff all in one.
