BlueStacks is an Android 2.3.4 Emulator for Windows and Mac that runs pretty fast even on slow machine. You only get one device though. It's purpose is to actually run the apps, but it is very usefull for debugging and testing using almost genuine Android 2.3.4.

Settings

The only dissadvantage of BlueStacks for me was the absence of settings, especially screen size and memory. This is important for games - you want to try as many screen sizes as possible. However you can set almost everything using windows registers:

 
[HKEY_LOCAL_MACHINE\SOFTWARE\BlueStacks]

To increase or reduce BlueStacks RAM, change the following value. I use 384MB, the default was 768MB:

 
[HKEY_LOCAL_MACHINE\SOFTWARE\BlueStacks\Guests\Android]

"Memory"=dword:00000180

And here is BlueStacks screen size:

[HKEY_LOCAL_MACHINE\SOFTWARE\BlueStacks\Guests\Android\FrameBuffer\0]
"Width"=dword:00000320
"Height"=dword:000001e0

You can of course try and play with all the settings, but some of them might break the emulator.

Debugging

BlueStacks come with USB debugging enabled, simply run the following command to connect with adb:

adb connect 127.0.0.1:5555

Installing APKs

Installation of applications is very simple. You can use Google Play Store, install the APK using adb or Eclipse. Or you can use BlueStacks AppHandler on Windows (Right Click->Open With option) to install it from Explorer (Mac probably has similar option).

Experience

BlueStacks runs very smoothly, ideal for taking videos. Sound works, OpenGL works.