I must have very different views than everybody else..
I don't like having a lot of calibers. If I shot you in the eyeball with a 9mm, you are DOA. Same with a .45ACP, .40SW, .32, .22 etc.. PLACEMENT is an overriding concern vs. caliber. That being said, a nice centerfire (9mm and up) will basically do the job.
I have decided to try to keep all my guns the same caliber if possible. So my current sidearm is a .40SW Steyr M40. My CCW when I move out of Kalifornia will be a Kahr P40. That way, I only have to buy 1 ammo, and I can keep a large cache of it, to drive down the prices since i buy in bulk. Now... The round I actually like, is the .357Sig. That being said, the beauty if buying a .40SW is that I can swap a barrel and have a .357Sig in any of my guns. So I have a good caliber, with the option to change to another caliber with a swap of the barrel.
I bought a bolt action recently, a Mauser in 308. Why? Because 308's are plentiful, I can get them ANYWHERE. I also have an M1A. That's in 308. See? 1 ammo, 2 guns.
I do own an SKS (that's because they tried to ban it here, so when I read that, I went out and bought one) I will try to acquire an AK47 at some point in time, so both guns will use the 7.62x39's. For revolvers, all my revolvers will be .357Mag. Why? Because I can shoot 38spls out of them all day long (which is what I prefer) but I have the choice of 357Mags if I want. .44Mag seems overkill, I guess I can hunt with it, but isn't that why I have a Mauser in 308, for hunting??
So I have no tried to have one gun of each caliber, but instead, I've tried to minimize the variety of ammo I have to buy.
For me:
Practice rifles(10/22) / pistols (22/45) ~ .22LR
Semi-Auto pistols (Steyr M40) (later, a Kahr P40) ~ .40S&W
Rifles (Springfield M1A, Mauser) ~ .308Win
Revolvers (SP101, GP100 next) ~ .357Mag (.38Spl options)
Spray and pray guns, (SKS, AK47 next) ~ 7.62x39
Also, in the case of Revolvers, I own a Ruger SP101 for my homeD, but I'm going to buy a GP100, because same action, same mechanics, and so I can learn 1 gun and have it apply to 2, the feel should be the same, and I will be use to it.
Same goes for the practice bolt action I will buy, probably a Ruger 77/22, so my 10/22 magazines will fit them.
Consistancy, interchangeability, and modularity. This seems the more scientific approach to things...
That's my suggestion, YMMV.