BlueStacks App Player is a clever piece of virtualisation software that will let you run Android apps on your Mac. The software has been available for the PC for some time, but has now made the jump, in alpha version, to OS X.
The software is free to download and, once installed, gives you an Android window in which you can run a selection of apps. That selection is currently restricted to 17 apps, so this isn't somewhere you can just dump APKs or install from Google Play, but it's a starting point.
The way that BlueStacks App Player works is that it offers a selection of featured apps, which have to be submitted by developers, with BlueStacks (the company) currently accepting only free apps. Once submitted to BlueStacks, it will include push the app APK into the App Player so that users can access it.
In the current selection you have the likes of Facebook and Twitter, the news reader Pulse and messenger WhatsApp, along with a few games. There isn't too much to get excited about at the moment, but it's early days.
Once open, the BlueStacks virtualisation window gives you home, menu and back buttons for navigation and then the apps run as you'd expect.
As an alpha build you can expect some hiccups, so this is one to watch, perhaps play with, but if you want Android on your Mac, it's free to download now.
Of course, you could use the Android SDK, but this is a nice simple approach.