Commission Jumction, in my opinion, is one of the best places to check out for all your Affiliate Marketing links. CJ.com has a wide range of advertisers in one spot and is very easy to use.
I will also tell you, DO NOT use Commission Junction or any other affiliate networks with Blogger Blogs. I found this out the hard way. I had a 6 year old Blog that was up to 4 figures in Affiliate income when Blogger shut it down for using Affiliate Links and there was nothing I could do to reverse their actions.
If you are operating a website or have a Wordpress blog with your own hosting, check out cj.com. You have to apply to the advertisers program and be approved so you need to build up some traffic before applying. Once approved by an advertiser, you can select different ad units that they offer. The usually have banner ads and text link ads. I always did better with the text link ads because in your articles, you can place a text ad that fits well and adds value for the reader.
There are many Affiliate Networks to choose from, but commission junction has good tracking and you can see how many clicked on the ad as well as how many times your ad was seen by readers. You can adjust your use of ads by how they perform. Oh, the most important part, payment was always right on time. Payment is similar to Adsense payments where once the threshold is achieved, your payment is processed.