This posting will be updated with external sources of information of power measurement.Sources of information on Home Energy Monitoring:
http://openenergymonitor.org/emon/node/156
http://forums.adafruit.com/viewtopic.php?f=8&t=22197
Sparkfun forum threads on the subject:
http://forum.sparkfun.com/viewtopic.php?f=14&t=29088
http://forum.sparkfun.com/viewtopic.php?f=14&t=28957
http://forum.sparkfun.com/viewtopic.php?f=14&t=28775&p=128925
Sparkfun products:
http://www.sparkfun.com/products/10341
Other products: