I've been challenged to try to find a bank account; I win the challenge if I can wire in $100 to the hidden account. Anyone have any good ideas about how to find an ABA number?

This sounds like the "this is your last chance to send me $1!" ad: Announcing the 'Bank Account' Hack. Rules: Wire me $100. Reward: I'll give you a T-shirt. The *real* challenge will be getting your $100 back.