As the cost of developing video games rises and game makers strive to reach a growing market of casual gamers, advertising – like it or not – is becoming an increasingly popular way for developers to increase revenue. Well, the ad-supported model got a further boost recently after Yahoo announced its plans to roll out more than 400 such games on its own gaming site by the end of this year.

The games, available as free downloads, will include titles from more than two dozen publishers and feature pre-, mid-, and post-roll advertisements delivered by Double Fusion and NeoEdge. The company still plans to retain the ability for users to continue receiving paid game downloads, sans advertising, hoping this flexibility will be key in satisfying gamers.

The move was one of several advertising-related announcements Yahoo made yesterday. The company also released a new service called “Build Your Own Search,” that shares its search technology with third parties in exchange for letting Yahoo display ads alongside the results.