As everyone has said you can make multiple offers, which require individual deposit checks. With the proliferation of bank owned properties, the timeframes on the contract don't always match the timeframes that a bank honors so communication is critical, and also respectful of the listing parties.
By that I am suggesting the following-
* When you make multiple offers be sure that it is reflected in the contract (as already said).
* If you receive a verbal approval of your offer, it may be a week or more before you actually receive the signed contract from a bank seller. That would mean a week before the deposit check is sent to title (since escrow info has not been communicated yet). It might be a good time to decide if you're going ahead with this contract or not.
* If you decide on one property, send a withdrawal of offer to all other parties so they do not leave you in consideration.
Good luck! It sounds like you're taking advantage of the good buys in this market.