[toni]

http://zferral.com/ has an easy build-it-yourself referral system.

[expertcs]

zferral seems to be a good option for affiliates who will continuously market your product. I am looking for a system which can help me release campaigns to my existing users. For example, if they post about my product with my link provided on twitter/facebook or simply email it to their friends and their friends purchase the product, I should be notified so that I can provide the offer to my existing user.

[jeffepp]

Hey Jeff Epstein, founder of zferral here..

zferral was actually built to enable companies to easily create their own affiliate or referral programs.

Nearly all of our clients use their custom program to create incentives for their own customers.

Remember, your current happy (paying) customers are your best advocates. We provide the tools for you to reward them to promote your product.

Anyone can feel free to email me with questions (or call). I'm happy to chat.