There are a few good gardening supply stores in Sacramento. Of these, GreenFire is one of the more specialized stores that deals primarily in hydroponic supplies. This store is one of the few places in town that you can buy everything from earthworm casting to guano, peat pots, meters, lights in various spectrums and sizes (watts), and much much more. Like a good hydroponics supply store, GreenFire has a good amount of supplies in a small facility.
Personal favorite Cocoa bean hulls -- but I love everything coffee related.