In general, an effective way to find a good affiliate program in an industry is to simply search the most high volume commercial search term and check out the top ppc bids. They are often taken by either the companies who offer the best affiliate programs or they are taken by affiliates themselves who are working with quality affiliate programs.
I'd recommend searching online for the programs through google or yahoo. For example, type in real estate affiliate programs or replacement window affiliate programs. You will find a large listed displayed. Networks are great for a lot of merchants under one roof as you say, but if you're looking for top commissions, I'd go to programs that have run theirs inhouse. Since they do not have to pay any fees to their network, they can pass on the extra $$ to you.