See recent updates (e.g. 2/10/11, 6/15/09), but also click on the Home Alone label in the sidebar.
The most frequently sought and read posts here at this blog over the years have been the ones on babysitting and, more to the point, When Can I Leave My Kids Home Alone? (Do you wonder? Parenting is not for the fainthearted.)
My previous post from Feb 2008 is here. Most of the links are still good, including the ones to the City of Albany, Clackamas County (look for the question: What is the legal age for leaving a child home alone?), and the Red Cross (this one on babysitting).