I recently created a catalog of products for Internet Marketers - you can get it free here: http://kickbutt.im/catalog-2012-winter.pdf

These are my products and I happen to have enough to be able to create and distribute a catalog.

But you don't need to have your own products. At the end of my catalog is a section where I link to books I have read and find useful.

You could create an entire catalog of useful products, specific to a niche, consisting entirely...