The app development scene is not lacking in activity, in light of the growing demand around the mobile sector, personal cloud and social enterprise trends. Many reports by research firms including IDC predict that billions of connected devices will be used worldwide in the foreseeable future – a huge chunk of which will be smartphones and tablets. This seems already true today, a fact which accounts for the over 600,000 apps spread across the iOS and Android markets.

There’s the matter of searching through all these apps though, and many companies are already taking a shot at monetizing a field that the existing stores leave wide open. Yahoo is now one of those companies, with the launch of  a new app search engine.

“Today, Yahoo introduced two new search tools, one a new online search engine for finding new mobile applications, and the other a mobile app called AppSpot (iPhone, Android), which does the same.”

Startups including Chomp, Quixey, AppStoreHQ, AppsFire, Zwapp, Frenzapp and others have launched similar products. The same goes for Yahoo’s Appolicous, which means that  Yahoo now has three correlative offerings targeting the same market.

Yahoo is looking to leverage the growth of the mobile app ecosystem, and so does Microsoft. A couple weeks ago it added a few social search features to Bing for iOS and Android users. These include app discovery, Facebook sharing, news, map integration and more.

In mobile, games seem to be the real money maker. Promoting these games to iOS users via a pay-per-install that offered incentives if they would download another app was mobile monetization company Tapjoy’s business. Apple didn’t like the thought of developers “buying” their rank in the top 25 apps list and started driving away developers from the company, which is why it has moved to Android. Now, Tapjoy started a $5 million fund to get developers to move their apps to Google’s OS.