Besides the three main alternatives AdWords (for example, Facebook, Yahoo! / Bing ads, and Amazon), there are many children who are still serving millions of impressions per month. One is Clicksor. Not the cheapest option, since it has $ 0.05 cents a minimum clicks, but is seo services a good result because conversions are known to be excellent. If you click are expensive, check your other ad formats that Clicksor offers as popunders and interstitial mixed CPM CPM or click +.
With respect to cost, 7Search is probably the most profitable ad network. It has low few clicks capita, high conversions (although this depends on the position), but also a large number of fraudulent clicks, as some dealers complain. However, even in these supposedly high number of click fraud, is still a very good alternative to Google AdWords.
AdBrite is another great network advertising and some vendors seo services say it works very well for them. The cost varies greatly depending on the keywords as well as an alternative, not necessarily very cheap (though the same keywords that cost much less than in AdWords). AdBrite offers great flexibility in the selection, many sizes and types of ads (text ads, banners, BritePic, ie cute photo ads), and conversions decent - what more could you want?
Bidvertiser is like AdSense and AdWords. It's another great network of sites issuers. What most distinguishes CPC Bidvertiser is relatively low with moderate to good conversions. There is an alternative for all positions, but overall it is a good choice.
Dynamic Oxygen is a relatively unknown ad network, but with some good deals. The same goes with Clicksor and AdBrite, offering many different species of PPC. Division PPC is not very expensive, but conversions could be a problem because oxygen dynamics are not that many places to match your ad, so that your ad may appear in places that are not strictly related to the location.