I usually buy bananas in a bunch of five and leave them on top of my microwave. Lately, no one has been eating them, and since they end up getting tossed in the garbage, I thought I'd try separating them to see if it would make a difference. I was pleasantly surprised that it, in fact, slowed down the browning!
Bananas also tend to ripen more quickly at room temperature. If you want to put them in the fridge, keep in mind that the skin of the banana will brown faster, but the banana itself will stay fresh longer than if stored at room temperature. Now you can enjoy a nice firm yellow banana!