Grease and cooking oil clog pipes and should not be poured down the drain.  For large generators, here's is a list of local and statewide grease haulers (from www.calfog.org):

Darling International:  (800) 4-GREASE or www.darlingii.com

Liquid Environmental Solutions:  (866) 694-7327 or www.liquidenviro.com
Portosan Santa Rosa:  (707) 566-2000
Rescue Rooter:  (800) 869-6917
Roto Rooter:  (800) 269-3747
All Valley Environmental, Inc:  (559) 498-8378
Ameriguard Maintenance Services:  (800) 347-7876 x14
Dependable Septic Systems:  (707) 645-1650
Modesto Tallow/Florin Tallow Co:  (800) 564-7204 or (209) 522-7224
One More Time:  (800) 624-5504
Sacramento Rendering Co:  (800) 339-6493
Sequoia Septic Tank Service:  (415) 451-1801

For disposal options for small amounts of grease or cooking oil, check out Napa Sanitation's FAQ page here.