In just under 4 minutes, this podcast is all about the different affiliate systems available, from third party to inhouse solutions. Software and solutions mentioned:

Hosted Affiliate Systems
Clickbank - only does digital goods
Shareasale - will do both digital and physical goods and works slightly differently - it's a pre-paid system
Digital River - popular with software products
MyAffiliateProgram

Affiliate Scripts
Groundbreak Affiliate System
iDevAffiliate - I've used this and it's quite good for one off purchases. If you're handing subscription or recurring commissions, I suggest you do not use it even though it's capable of it - but I found the recurring commissions confusing.

Third Party Affiliate Systems
PayDotCom - I use this too. Point and click easy
1ShoppingCart - The best, can be quite a learning curve
ThirdSphere - Get it all in one

MP3 File