I usually use a combination of reports

www.kbb.com
www.nada.com
www.edmunds.com

I find the rough average of those three reports, and then I check out www.autotrader.com to see what these cars are ACTUALLY selling for in my area.

- Zack WANTED: T-Red HEATED Side Mirrors FOR SALE: 4 14" Alum Alloys and Nearly New Avid H4s Tires w/ Center Caps 2000 T-Red SVT 1995 LX V6 MTX (RIP)