Apart from Googleplay, the following websites are useful in promoting yur Android apps:
https://developer.amazon.com/welcome.html
http://www.appbrain.com/info/addapp
http://slideme.org/developers
http://developer.getjar.mobi/
Check out the following article for complete information:
http://www.shoutmeloud.com/how-to-promote-android-app-game.html