You may want to check out HostingCatalog.com as an AdWords alternative. The minimum bid there is only $.05 and they also have an ad network with bid prices around $1.00, which is a lot less than what you would spend in AdWords.
I completely forgot about this option! It is indeed true they offer ppc advertising placement. However, top positions cost up to $3-4/click.
I am curious to find out how HostingCatalog.com compares to Google AdWords in terms of traffic generation effectiveness. Say, you are a top bidder for "shared hosting" category, and you are ready to spend $3/click, how much traffic do you actually get out of it?