A lot of discussion revolving around which is the best. IMO Adsense all the way – you know you’re going to get paid and the ads appear on your site given it has a bigger advertiser network than the rest.  Thats not to discount the rest of the other PC networks, but I have read things about Adbrite (which seems the most promising alternative) and Bidvertiser that make it hard to convince me from straying from AdSense.