Windows/Android: If you've ever wished you could test out Android apps before installing them on your device or just want to use the same apps on both your Android device and your computer, check out the free BlueStacks App Player.
Currently in alpha stage, BlueStacks runs Android apps in full screen on Windows 7 and comes preloaded with 10 apps, including news reader Pulse and several games like Bubble Buster. You can install up to 26 more apps, but you'll have to connect to the BlueStacks App Channels with Facebook.
I tested BlueStacks on a tablet PC and the apps worked, though a bit slowly probably due to it being an older netbook. Having a touch interface is ideal for running Android apps on your computer, but without one you can still get a feel for an app with your keyboard and mouse.
The App Player also syncs apps between your PC and your phone or tablet if you install the BlueStacks Cloud Connect App from the Market onto your Android device. This could be useful when you want a (sort of) seamless experience going from your Android device to your computer and back.
A version for Mac is in the works, as is a Pro version of BlueStacks App Player will let you play premium apps like Angry Birds.