If you've ever thought of starting your own affiliate program THE standard for affiliate scrips is idevaffuliate. I would say that when I sign up for an affiliate program, 70-80% are using this scripts. It's awesome (I've used it in the past on websites), the tech support is awesome, and its affordable. You can have as simple or as versatile an affiliate program a you want.
The best thing is NOW is the time to purchase idevaffilaite as you can use the discount code springtime8 and save 8% on your purchase. The software starts at $99 and the discount code expires at the end of June so don't delay. For more information go to idevaffiliate.com