There isn't really an exact answer and it will depend upon who you are recommending the product to and for what purpose. Programs like Hostgator, Host Monster and Blue Host pay very well for NEW referrals to their hosting programs. You can sign up as an affiliate for free at any or all of them.
Their are some MLM programs or marketing programs like GVO who require you to be a member. These programs will be unattractive to the vast majority of people seeking hosting to run their website on and are only attractive to other online marketers.
The other option is the Site Build It affiliate program which offers a unique way for customers to build their sites from an SEO perspective from day one.
Ultimately the program you recommend should be the one you personally use or have used yourself. You then can speak with some authority on the subject