#1 - Day job (in-house SEM) #2 - Consulting #3 - Adsense Adsense used to rank higher, unfortunately. Sites got nuked.
It varies a lot website to website for me. Some websites make nothing in one area and a lot in the other. Overall I'd have to say affiliate products though.
My main source of income is from paid customers but after that it is affiliates, then AdSense, then AdBrite. I have yet to explore other ad networks.