Best value is unquestionably an SKS. Yugoslavian-production SKS's can be had in the $100-$150 range, rendered CA-legal by replacing the grenade launcher with a muzzle brake. A 10-round, clip-fed magazine is standard, and is very efficient with practice.
If you want to spend a bit more money, there are the Ruger Mini-14 and Kel-Tec SU-16CA, both in 5.56mm. Both are good rifles, but the Kel-Tec has the advantage of having 10-round mags as standard, compared to the Ruger's 5-round mag. The Kel-Tec can also accept standard M16/AR-15 mags, if you happen to have some pre-ban hi-cap ones lying around (or if you should need to rely on another source of mags and ammo in a trouble situation).
You could also look at a lever-action carbine such as the Winchester Model 94 or the Marlin 1894/1895/336, in various calibers. These are fine weapons, and I'd feel very well armed with one of them in .30-30. The tubular magazines hold less rounds, and are slower to reload, than the semi-auto's referred to above, but this is only a factor if you're in a hot firefight with lots of rounds going downrange.