If you want to advertise your blog for free, you should try out Adgridwork and Adleaf. Adgridwork and Adleaf are giving a free, open advertising network and allow bloggers and other website owners to submit their ads into their ad network. In exchange for serving your ads on others related sites, they would require that you in turn serve ads for other users. The end result would be a giant community of websites that would all help one another promote and market their products, ideas and service for free

Adgridwork and Adleaf offer free Contextual Online Advertising and Online Advertising Networks that provide a service that will automatically distribute your ad copy across their network of blogs or websites that are contextually relevant to your own.

See example of the ads:


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