Targetz has a large list of free printable targets. So does My Target and Reload Bench All this goes to show that finding good shooting targets is tough, especially if you want them on the cheap.
Your typical cheap target has a lot of black on it and rapidly develops contrast issues. You can't see the black holes you are making on the black areas of the target. At least not from 10+ yards away in poor light on an indoor range. And you don't have a good aim point because the center of the target is a large black circle. And they are made from the thinnest paper possible so they tear.
Then there is the ever-popular silhoutte target. They're expensive. They're huge. They're often all black with poor contrast. And despite their size, you can only shoot on them in two places per target: the head and COM. They're over-rated and over-used in my opinion. But gun ranges love them and love to sell them cause it is money in the bank.
I switched 100 yard rifle zeroing targets pretty early on. You can get these or a variant of these at most sporting goods stores. Typically these have a nice red and white pattern so bullet holes show up well. You also typically get 5 targets on each sheet, so if changing targets is a pain (like at an outdoor range) then thats more fun per target reset. The problem is that you still often lack a good point of aim. All that red and white just turns into fuzzy blur when you're concentrating on the front sight. You can fix this cheaply and easily with a black magic marker by putting a big dot at the center of each pattern on the sheet. But that black dot has the bullet hole contrast problem, so if you shoot very well then you don't know how well until you can take down the target.
Shoot-N-C targets don't have the whole bullet contrast problem. They are constructed so each bullet develops a bright ring (usually green or orange) that contrasts nicely with the rest of the black surface. Most of these targets come with a single large stick-on disk marked with concentric rings and a few very small unmarked disks. The large disks are great for covering up areas on a target that you have completely shot out. The smaller ones are great for marking an aim point. I know I'm shooting well when the only thing I'm hitting at 7-10 yards is the little marker disk. Shoot-N-Cs are great for teaching new shooters because they can see exactly where the bullets go. But they ain't cheap for regular use.
I recently ran across a new brand of rifle target that is black on yellow paper. It is my current favorite. The holes show up well because the black lines aren't thick enough to obscure them. Aiming is easy because the target is black on yellow. 5 target patterns are on each sheet and they're good paper yet pretty cheap. I just wish I could remember where I bought them.