Affiliate program directories are listings of sites that offer affiliate fees for selling their products. Many small sites offer affiliate commissions and run their own affiliate programs. Search for affiliate programs that are related to your niche market (be it cooking, books, or camping).
No matter what area you want to start an affiliate business in, you can find an affiliate directory of related businesses. Look for affiliate-oriented online forums as well. Tell them the topic of your web site business, explain a bit about your background and why you're interested in this, and then ask for recommendations. Most people are happy to plug their favorites.