Ever wish StumbleUpon suggested things other than websites to you? It looks like they are working on an answer to that with the latest beta of their Android app. Now, not only can you stumble onto websites you might never have found, but you can use the App Discovery feature to find those rare gems from the Android Market.
App discovery works by analyzing your app library (after you have given permission) and comparing to other users with similar tastes to suggest new downloads. As it is now, it is understandably a bit buggy, but with some improvements this could really get cooking. The Android Market is admittedly a bit hard to navigate and sift through at times, so a suggestion service like this should definitely aid in finding quality apps.