I just attended a seminar with Jeffrey Otteau, Fortune 500 Appraiser in NJ, so this information comes from him, not me. On average in NJ, prices are back to the 2003 level. If you bought in 2003, it's a good ball park idea of where to price today. Unless the condition of the street and/or upgrades has declined since 2003, what you paid in 03 is what you can list for in 08.
As for the decline, again this is an average statistic, it is 1/2%/month. So if your house today would comp out at 400,000, then next month it would be worth 1/2% less or you would price it at $380,000. Here's the real kicker: Houses that are priced right sell for more money in less time. In other words say your house is worth 400,000 and you price it there. A similar comp prices it at 425,000 to "allow for lowball bidding", etc. Jeffrey's research shows that the person who prices at 400,000 will sell for more $$ and in less time than the similarly priced home only $25,000 more. If you would like to see these charts, you can email me and I can fax or scan them to you.
The most important factor is to get an agent who understands the market. As I told you, these stats regarding 03 pricing and the 1/2% decline are NJ averages. Each town is different and a local agent can help you. In my main market of Spring Lake, in 2007 more houses were sold than in 2006 and for MORE money (on average.) So, you can see how each market really is location specific.