There are hundreds of energy, water, and waste incentives, rebates, and services available for homes in California, but it can be daunting to find them. Here are a few places to start:
Flex Your Power allows you to search for energy-related incentives and technical help available from utility companies, water agencies, and other organizations by entering your zip code. A search in my zip code (in Berkeley) found 71 incentives and 18 services.
The Database of State Incentives for Renewables & Efficiency (DSIRE) lists state and local incentives by category and also lists related programs and initiatives. It can be much harder to figure out which specific programs are applicable, though. The database also lists federal incentives.
The California Urban Water Conservation Council lists programs participating in its Smart Rebates by water utility district.
For folks living in the East Bay:
East Bay Municipal Utility District lists its residential conservation rebates and services.
StopWaste.Org lists waste prevention and recycling services available to residents of Alameda County.