It has been reported that it is better to use Yahoo to reach non technically minded people compared to Google.  Rentacoder.com for reverse auction on software projects.

Arbitrage involves buying clicks to get visitors to your site. Once they are there, then you hope that they will click on the Adsense or other monetizing ads that your site has. For example you can buy long tail clicks at a LCPC (low cost per click) and intend that the visitors to your site click on more competitively bid ads on your destination site. Or you can use a search engine which does not charge a lot per click and then direct that traffic to a site which has higher priced clicks. I have experimented with Miva for this purpose, and got lots of traffic that I paid for but nothing that converted to a click on my site. I also tried signing up with Superpages PPC, but they require a business phone number to get started.

Google Adwords will penalize you if your destination site is not enhancing the user's experience, i.e. it just has ads, or there are no links from that page to other sites or to other pages on your site, or the keywords you are bidding on don't appear on your site. This is according to Michael Plante, a Google arbitrage expert.

He also advocates having less ads on a page, so that there is more chance that a high paying ad will be clicked.  Most of his advertising is aimed at the content network because it is cheaper.

His technique is to select the keywords that are the top 6 paying for a particular keyword niche using something like Keyword Elite. These will be used to create the Adsense page. He will then take those 6 keywords and get the 6 top related keywords related to each of the 6 top paying ones and these are what he uses to build his Adwords campaigns. So it works like a funnel, with the less specific keywords funneling through to the more specific higher paying ones.

Yellow Pages, TV, radio are all ways to generate traffic.