Application Launcher for Drive is a browser add-on that allows you to open documents from Google Drive from any program on your computer.
When you access your documents in Drive in your browser, simply right click and chose 'Open With'. You will then see a list of compatible programs you have installed. The 'Connect With' option then allows you to add any programs that aren't in the list and suggests software that you can download to open the file.
It's a simple concept but it works really well.