No good zombie survival site would be complete without a discussion on the firearms you'd stockpile, and what's suitable in a survival situation. Personally, I'd want at least one shotgun (12 gauge), one semi-automatic rifle (I'd love an AK variant, but the M1 Carbine seems like it would do a good job), and a handgun of decent caliber and stopping power.
The Zombie Survival Handbook recommends .22LR rifle and sidearm because it reduces the weight and types of ammunition you have to carry. I'm not sure I agree because Zombies are the least of your problems, especially since early on you're likely to deal with panicky humans flailing around being stupid and then later probably raider/pirate/brigand types who are looking to resupply.
I don't think we're talking about everyone being a cowboy, since that stereotypical figure would probably wind up trying to "go it alone" and get themselves and possibly others killed. I do think each person would need to train with a weapon of choice, and get at least familiar with the basics of firearms.
Personally, I don't think I'd want a handgun with less than a .40 caliber round, with the possible exception of the .357 Magnum. The magnum's limitation is the amount of ammo in the pistol at any given time...that's also a strength since you'd want to make each shot count. It'd be way to easy to blow through a fully loaded magazine in a panic situation. I think a 12 gauge pump action or semi-automatic shotgun would be fine. you can pick those up at just about any wal-mart. That's the strength of the .40 and .45 rounds...most everywhere in the US carries that ammo type. Picking a rifle would be the toughest I think, since you'd really want to balance power, accuracy, durability, and availability of ammunition. To me, that balance is found in the AK-47, though I'm sure there'd be plenty of arguments about that statement.
Could you make room in a group of survivors for people who refused to pick up a firearm no matter what? And when it comes time to rebuild society, does that mean the ones who rebuild society will necessarily be militaristic and disciplinarian? Maybe they should be?