For those of you who live in houses, I strongly encourage you to park your car on the lawn and wash it there. This prevents large amounts of soap (and other nasty chemicals) from ending up in Putah Creek. It also uses "waste" water to water your lawn, saving water, one of the most valuable resources. Don't worry, it won't hurt your lawn.
Most gas stations will give you a discounted car wash if you purchase a certain amount of gas. In general, the cheapest option does not include drying.
Arco / AMPM - on Mace Blvd.
Chevron Extra Mile - on Chiles Road
South Davis Chevron - Fully automated (like a conveyor belt)
Davis 1 Stop - 76 Gas Station on Covell Blvd. by Hwy 113
Independent Car Washes
See Consumers Guide for car wash coupons.
Auto Washette - Coin-operated
Cable Car Wash - Full service. $7 for exterior.
Li'l Bear's Car Wash - Full and Self services
Planet Wash - Coin-operated or credit card. $2.50 minimum, usually takes about $5 to fully clean the exterior.
Sundance Car Care Center - Full service (in Woodland)
"Free" Car Washes
Every so often you'll see someone outside of Save Mart holding up a sign advertising a "Free Carwash." This is usually a frat or club trying to raise money though donations. I don't know if they'll wash your bike. The local churches on Anderson have also had free car washes, only they will refuse donations. Apparently there are statewide contests to see which youth group can wash the most cars for free. In 2003, they competed for a trip to Mexicali. Their advertising practices, i.e., jail-bait bouncing up and down in bikinis, is somewhat shady.
Often during the Saturday Farmers' Market, there will be similar free/asking-for-donations car washes held by various high school groups in the parking lot at the corner of Russell and C St.. (Sometimes these charge a small fee, so check the signs).
Davisville Express Lube offers "free" car washes during the summer if you get your oil changed there.
There is a free, automated car wash in Fleet Services, but it's only for university vehicles.