For the 22nd year in a row, Remodeling has released their annual report on the relationship between remodeling costs and resale value. Their report allows you to compare national and regional averages for 33 popular remodeling projects; you can also download a PDF with project data for any one of 80 U.S. cities. They also provide links to prior reports from 2008-09 back to 2002.
Click to view report: Remodeling 2009-10 Cost vs Value Report
This is a great reference and is a very useful tool if you need a general idea of the cost-to-value relationship for many popular remodels throughout regions in the US.
Remember that these reports are based on large geographic regions and may not provide detailed information for your specific location and real estate market. For a more focused analysis of the relationship between cost-to-value for your individual property, you should consult with a local certified real estate appraiser who is familiar with your particular market and neighborhood.