Buying a classified ad on eBay and making a video for youtube can have a decent return as far as traffic goes.
A lot of people are using Craigslist to promote Amazon products. You should do a search on Google, or just read around this and other webmaster/internet marketing forums. There's a lot of ways to promote Amazon affiliate products and make money with their program, you just need to do a bit of reading.
try Google Adwords or Yahoo PPC to get started, but beware of the CPC's as they tend to be very high for competitive products.