As of 1 April, there are:

Federal:

Federal Tax Credit or 30% or upto $1500

<http://www.energystar.gov/index.cfm?c=windows_doors.pr_taxcredits>

San Diego County:

SDG&E Rebate Program $200 for 92% and up qualifying furances.

<http://www.sdge.com/residential/centralFurnace.shtml>