If you're just going to shoot targets, you can easily narrow down your choices:
Autos: .22 or .45 (I own a .40 and would not recommend one for target shooting for numerous reasons)
Revolvers: .22 or .357 (don't listen to lazs)
The .40 is a nice comprimise gun between a 9mm and a .45, but it doesn't have the target support that a .45 or a .22 does. Those two calibers are pretty much the standard for autos.
The .22 and .357 revolvers are even better for target in that they have better accuracy than the autos do. The .357 is nice because you can shoot .38 out of it all day. Both calibers of revolver also have alot of support in the target shooting community... though the .44 would be there too.
The .40 is great if you're actually looking for a concealable weapon. But when it comes to shooting paper, there's just alot of better options out there.