Adreporting.com - Sign up for free.  Advertising information is provided for you to put on your site or pay per click ads.

Commission Junction - I've been with Commission Junction for several years now.  They have an amazing number of companies to work with.  Find your niche, and start marketing the products you like.  Sign up is free and you have thousands of offerings to choose from.

Linkshare - Similar to Commission Junction.  Tons of products and services.  Join all three of these affiliate programs and pick your favorite products and services to market.

Not all companies go through the big boys I've described above.  Lots of companies run their own affiliate programs independent of the larger networks.  Don't overlook these players.  I've described a few of the better independent programs below:

VMCSatellite - Exploit this niche and get paid when a visitor gets a Satellite dish installation.  This is a huge market in rural areas as well as a great alternative to cable TV. Several affiliates are making thousands each month promoting this company.

AllPosters.com - Some affiliates are earning between $2,000 and $5,000 a month promoting posters on the internet.  That is a full-time income for part-time effort.  Put this bow in your quiver for making extra cash.

Real Casinos - Online Casinos are money makers, and they are willing to pay you big bucks to bring them players.  Real Casinos has a list of the top paying online casinos - definitely worth checking out..