StumbleUpon, which is one of the largest social bookmarking sites, currently sells targeted visitors at just $0.05 each.
After you create a campaign it takes about 24 hours to approve. Once approved, funds can be added by using PayPal.

StumbleUpon also produces from pretty graphs, showing the number of visitors and also the number of “thumbs up” and “thumbs down”

After purchasing a campaign for another site, a $65 (1300 visitors) campaign delivered more than 2100 visitors (or about $0.03 per visitor). Why? Because “Using the StumbleUpon toolbar, members rate content “thumbs-up” (really like it) or “thumbs-down” (not for them). The more people who vote “thumbs-up”, the more quickly it will spread. Well designed and targeted content often starts to spread virally through StumbleUpon. The more people who see it, the more they pass it on to their friends (both within and outside of StumbleUpon).” Thus, the people who gave the site a “thumbs-up” diverted more traffic to the site.

Overall, the traffic wasn’t the highest quality (many users left or “stumbled” another site quickly), but there were some users who ended up staying on the site. After everything had been completed, there was a positive return on investment.

I'm shocked & dismayed. Well, not really, but I had no idea stumbleupon operated that way.

Stumbleupon is somehting I have tried before but to be honest the raffic is the most untargeted traffic you can get just think...

Its called stumble upon and thats what people do... dont waste your time unless your product appeals to a big market

Josiah

This is a good way to promote a new web site, however if you are looking at making substantial revenue for those users then I got news for you, this traffic is absolutely worthless. Stumbleupon users have a habit of clicking stumble as soon as they loose interest in the site.

Do you mean that they don't separate the users they send to you based on their categories? For example, stumbleupon has categories for travel, web development, etc.
Let's say I am the founder of a general travel site with a cool new twist like Mobissimo and I start a campaign on stumbleup. Can't I select "travel" as the kind of traffic I would like? Or is that not how it works?