hi,
if you're using affiliate marketing as a business model (ie. selling other people's products), you'll be going to affiliate networks quite a bit.
the big guys are
clickbank (clickbank.com)
commission junction (cj.com)
paydotcom (paydotcom.com ---yes, one of the most 'interesting' URLs).
the payout is much higher than for web ads like adsense/adbrite.
and some affiliate marketers (a subset of internet marketing) are making in the range of hundreds of thousands of dollars a month in sales.
the payout from affiliate marketing is anywhere from about 40% to 90% of the sales value.
i have included some info at
www.internetmarketingcookbook.com.