PV Watts is a great tool for estimating what your power generation will be.  You can experiment with lots of different variables.  http://www.nrel.gov/rredc/pvwatts/version1.html

DSIRE:  Database of State Incentives for Renewables and Efficiency.  Don't let the name fool you - they cover Federal programs too!  This is by far and away the best resource out there to help you find out which incentive programs you qualify for in your area.  I've always found it up to date and accurate.  These folks are geniuses.  http://www.dsireusa.org/index.cfm?EE=1&RE=1

Kill a Watt:  We used this device to determine which appliances were really costing us in our house.  http://www.p3international.com/products/special/P4400/P4400-CE.html

Carbon Calculator:  There are many to choose from.  Here's my favorite: 
http://www.epa.gov/climatechange/emissions/ind_calculator2.html#c=homeEnergy&p=reduceWaste&m=calc_instructions

Carbon offsets:  http://www.carbonfund.org/

Nitrogen Calculator:  This tool, developed by the Chesapeake Bay Foundation, shows you how your choices (including electricity!) affect the Bay.    http://www.cbf.org/yourbayfootprint/

Natural Gas Calculator:  http://www.minnesotaenergyresources.com/home/gascalculator.aspx