Highly professional site with some well known brands. Clients include: America Online, Blair Corp., Bose, CompUSA, Eddie Bauer, HP Shopping, Kohl's, L.L.Bean, PC Connection, RedEnvelope, Verizon Wireless, and more than 200 others. Formerly known as Performics, which was bought by DoubleClick, which in-turn was bought by Google.

ShareaSale (www.ShareaSale.com)

I would highly recommend ShareaSale, due to its unique qualities. Its a large network offering hundreds of programs – pay-per-sale, pay-per-lead, and pay-per-click programs. More than 700 merchants. It has a strong pro-affiliate attitude and despises parasites and lots of datafeeds. Highly recommended for beginners.