I don’t know that I would suggest this pricing strategy, but it is interesting.  There is a coffee shop (Terra Bite Lounge) in Washington state that has no prices, but instead has a donation box.  The theory is that peer pressure, guilt, and common decency will cause the consumers to give appropriately (or more than appropriately).

Here is a link to the Seattle Times article, but I would suggest that you go to the Freakonomics blog where there is an interesting discussion going on in the comments.  Apparently there are several other businesses that have tried the same approach in different parts of the world — with different results.