You may find that the craigslist free section has many listings for free soil/dirt. If you're using free soil for your farm/garden, beware that most of the free soil on craigslist (even the kind marked "clean") is not appropriate for farms and gardens. What you're looking for is compost or topsoil. Fill dirt is not very good for gardening.
Options for free soil (not fill dirt)
- Berkeley compost - you need a Berkeley address for this so if you have friends in Berkeley, bring them!
- Annie's Annuals Saturdays and Sundays, 9-noon. Soil is piled at the rear gate of the nursery, first come, first serve, bring your own bins and shovels.
Options for very cheap soil (not fill dirt)
Compost from the county recycling center in San Leandro is $24 per cubic yard. It's at 2615 Davis Street, San Leandro, http://wmearthcare.com/availability-pricing/
Monday-Friday, 7am – 5pm
Saturdays, 8am – 4pm
Notes on size and how to get the soil back to your place
Many of the craigslist free listings say "minimum of 10 cubic yards" - that's a lot of soil. It's about one dump truck full of soil. An everyday pickup truck can comfortably carry about 1 cubic yard of soil. For all of the above listings, you pretty much need to bring a pickup truck or some other similar thing to get the soil back to your place.