After trying quite a few android apps, I found Camera Illusion and stuck with that (free for basic version which I exclusively use or you can get the pro version for more features at a price that I'm not sure of, never bought it). This is just a simple photo app with some basic effects and filters, I'm pretty sure you'll be happy with it. Give it a try. It uses the volume keys as the shutter-button which is really handy in my opinion. I have an HTC Droid Eris and have been using that photo app for almost as long as I've had the phone, about two years. Here are a few photos that were taken using that app and the horizontal-mirror effect: