Priceline is famous for its Name Your Own Price (NYOP) program, which can often provide significant savings on hotel rooms. But, one of the cardinal rules is that NYOP reservations are NON-CANCELLABLE. However, this blog post reveals a trick that works.
The comments to this blog post are very instructive.
The idea is to call the hotel first and get them to agree to a cancellation. Then call Priceline, tell them the hotel has agreed to cancellation and give the name of the hotel person. A Priceline representative will call the hotel to verify, then refund your money.