How can I speed up banana ripening? I need to make banana bread tomorrow, and the bananas I recently purchased with this in mind to not appear to be ripening fast enough. Is there anyway to speed the ripening without spoiling the bananas altogether?

(I have looked at this answer and it refers to how the fridge will speed up "blackening". @Sarge_Smith describes it as a different process chemically, so I am unsure that blackening == ripening for the purpose of making banana bread.)
Bananas are imported unripe and then ripened in the country of sale. This ripening is achieved by forcing ethylene gas through the bananas in special pressurised rooms.

Bananas naturally produce ethylene as they ripen, so you could just put them in a sealable plastic bag to contain that gas. Tomatoes also produce ethylene, so you could pop a couple of those in as well, but be aware that they'll also ripen faster too.