Youtube's partner program allows you to place Adsense ads on your videos. In order to do this, your videos must be A) highly rated and B) have a lot of views. You must have an Adsense account in order to do this, and other ad types are not supported. As with all Adsense ads, you get paid for every time your viewers click on the ads. The ads can also be hidden, so that your viewers don't have to see the ads if they don't want to.
Metacafe's publishing system has more definite requirements than Youtube's, but the potential for payoff is different. As long as you hold the copyrights for everything in your video, or have permission to use copyrighted material, you can submit your video (you can pick and choose) to the program. In order for your video to be accepted, it must meet two requirements. First, it must receive 20,000 views in the six months after being submitted, and second, must have a rating of at least 3/5 stars. If and when your video meets these requirements, you will receive $2 for every 1000 views. It may not seem like a lot, but remember, if your video receives 20,000 views in under 6 months, you will quickly begin to earn money. Your sent a check once your balance reaches $100 USD.
Blinkx ad program lets publishers put ads on their embedded videos (not necessarily theirs) , and the revenue is only split between Blinkx and the publisher. Payment is made through PayPal, and this program is usually the most successful through social sites like Digg.
Each video uploaded to IMCandy is attached to 5 second video ads (the amount varies depending on video length). The publisher receives 30% of what the advertiser pays, eliminating the middleman. As the average cost of ads is $20 per 1000 views, and 30% of $20 is $6, publishers can stand to earn a pretty heavy profit.