For those of you who visit my site regularly you will find that I've added a "bank approved" short sale list. Having bank approval prior to making an offer can potentially save several weeks of waiting and wondering. You can expect to receive an answer to your offer from the bank in less than a week. Another bonus is that the banks loss mitigation officer typically has authorization to make a counter-offer vs. approved/denied.
Every bank and every property is different so I can't give you fixed time frames for response from the bank. As is the case with foreclosures, every offer must be submitted on an as-is contract and accompanied by a strong letter of pre-qualification from a reputable lender.
I've also added a market statistics tab to me website - it's worth checking out! I will be adding to it and adjusting the figures to reflect current market activity periodically.