I've heard putting them into a brown paper bag works
Nonono! This will make them ripen /faster/!
Bananas give off ethylene gas (a plant hormone) as they ripen, which acts to stimulate /further/ ripening. If you trap them in an enclosed space (like a paper bag), the gas will accumulate and speed the ripening process.
You can use this to your advantage to help ripen things like tomatoes... when I pick near-ripe tomatoes off my plants, I generally toss them in a paper sack with a banana.. they ripen much faster!
But that won't help /slow/ the ripening process.
Your best bet is to buy a banana hanger (... not a speedo!

) and keep them in a well ventilated area to ensure that the ripening gases don't built up around them. And don't stick them in a pile of other fruit, as the gas will speed the other fruit's ripening up and will quickly cause it to spoil.
By the way, if you peel & wrap them tightly once full ripe.. you can also freeze them for later!
And you /can/ put them in the fridge (only if fully ripe, though!)... they WILL get ugly, but will still be edible. The cold will slow the ripening process some, but will encourage the 'blackening' enzymes in the skin.
=)
Edit: I can't believe I forgot to add this...
