If you are in the position to cash-buy, a new build property can be snapped up at around 50% of the asking price as developers are on their knees for working capital and lending is drying up in this particular segment of the market.
Otherwise, the amount you get off the asking pice will depend on the desirability of the property. Some properties will be affected by the banks' reluctance to lend and the economic slow-down more than others. Unfortunately, for people who are still waiting to get on to the ladder, there is still a sizable demand for first-time type properties and the discount here are still likely to be negligible...
It also depends on factors such as whether you are in a chain and how desperate the vendor is to sell the property.