Adengage has shown amazing promise since it started up several years ago. The site has some of the most advanced bidding and advertising techniques within its grasp and holds a fantastically high conversion rate from impressions to clicks. Despite the fact that this has no referral program I have to recommend this as a fantastic affiliate scheme.
It will show adverts on practically any (legal) website and gives you an amazing 75% of the profit, a fairly good amount ompared to some affiliate schemes.
Its downside is that it does not have quite the same range of advertising options as clicksor. This is not a problem though if you only intend to use banners on your website.