What are the most profitable affiliate sites and what are the best ways to advertise them?

This is a hard question to answer, there are numerous ways and methods. I would start by reading Revenue Magazine, they are the best publication for affiliate marketing, pay close attention to their advertisers as well (for potential programs to promote). You can pick it up in almost every B&N/Borders.

Check it out here: http://www.revenuetoday.com

the best comapnies are CLICK BANK

S F I then google adsense but adsense is peanuts in income

go here to my site it is free to join either comapny and they are B B B registered

YOU do not need a website or pay anay fees or but anything

YOU get full training and support from proven internet Millionaires

plaus i have free advertisng software and links to advertise YOUR links too !

Go Here

http://home.comcast.net/~billyzeke

watch for my websites to be ranked in next two months in Google Yahoo MSN and Open directory serach engines and directories