Android: Facebook is easily one of the most widely used apps on any mobile platform. If you want to see what's coming down the app pipe before anyone else, the company has both beta and alpha channels you can sign up for.
This will already get you ahead of most users, and you should probably stop here if you want something remotely stable. Of course, you're on Lifehacker which means you love to push the boundaries. In that case, the company has also launched an alpha channel that you can sign up for here. Keep in mind that this could result in a lot of instability if you need Facebook on a daily basis.