I bought a new boiler to heat my home in 2009. Can I take the Residential energy credit?

Yes, as long as it is a natural gas, propane, or oil fueled boiler with an annual fuel utilization efficiency rating at least 90 (or 95 if placed in service before Feb 17, 2009). See instructions for Form 5695: http://www.irs.gov/pub/irs-pdf/f5695.pdf