From our friends at Natural Home Magazine:

Net metering:  A method that allows homeowners' electric meters to turn backward when they generate more electricity (via solar panels, for example) than they use.  When electric meters turn backward, the customer receives retail prices for the excess electricity generated.  Without net metering, a second meter usually is installed to measure the electricity that flows back to the privder; the utility company purchases the power at a below-retail rate.

Two of my favorite solar websites:

http://www.chicagosolarpartnership.org/index.php?src=gendocs&link=HomePage

http://www.illinoissolar.org/