With more than 100,000 iPhone applications available it can be difficult to strip out the right ones for you. While Apple offers several possibilities to search and find applications it can always be better. 
Chorus is free app for iPhone that can show you the applications that your friends are using.
Chorus mashes together App store with social network. The program connects users with friends by social networks like Twitter and Facebook.
Chorus is fun and free way to discover hot new iPhone apps from the people you trust most – your friends!
Users can get Chorus apps they have purchased with friends and stay informed on what apps friends buy and what they think. It allows users to discover new applications. Chorus also gives recommendations on apps themselves with good ratings.
You can download Chorus app free here
I like Appfinder a lot better. Not as much feature bloat!
http://www.theappfinder.com/