You can create:
- 1 subnet containing 64 addresses (/26)
- 2 subnets containing 32 addresses (/27)
- 4 subnets containing 16 addresses (/28)
- 8 subnets containing 8 addresses (/29)
- 16 subnets containing 4 addresses (/30)
- 32 subnets containing 2 addresses (/31)
- 64 subnets containing 1 address (/32)
Given that a IP subnet always has two reserved addresses, the lowest one (network) and the highest one (broadcast), and so needs at least two more addresses to be actually usable, the lowest number of addresses you can have in a "real" subnet is 4.
Of course, you can also mix them, because every subnet can be re-subnetted; so you could f.e. have a /27 subnet using up the first 32 addresses, and two /28 subnets using the remaning 32 ones, dividing them in two blocks of 16 addresses. In any case, by using more smaller subnets, you are going to waste more addresses (due to each subnet requiring two reserved ones).
As usual, you can find everything you need to know (and much more) here.