What many list owners end up doing is creating their own products (if they don't have them already).
This gives you ultimate control over what you're offering to your subscribers, as you are the one who decides what goes into the product. This is amazing, because after a while you will have gotten a feel for what your subscribers really need and want. This allows you to zero in on their wishes and hand-deliver them a product you know they'll be happy to pay for.
It can also be more beneficial to promote your own products, since you don't have to split the commission as an affiliate. This can be more lucrative in the end. Having your own product can also brand you as an expert. As soon as people see your name on a book or other product, they know that you are a serious person in your field.