Bungy/Sandal Bindings
If you have a wakeboard which heaps of different people of different foot sizes use then you might be best to get a sandal/bungy bindings.  These are typically suited towards the beginner - recreational and allow everyone to have a go (usually sizes 3-12).

They are also very cheap, but beware - you do get what you pay for and often they are prone to breaking. Also they provide very little support and you start spins and decent jumps you will need to upgrade to a more supportive binding.

Adjustable Boot
Another option if you need a binding for many different foot sizes are adjustable boot bindings, such as the Hyperlite Shifter or the OBrien Sport Morph Adjustable (pictured). These types of bindings provide much more support than bungy bindings but still allow for many different foot sizes, usually through an adjustable toe piece.

High Back/Boot
These Bindings are the most supportive of all, what they lack in easiness to get on they gain in supportiveness and comfort.  These are perfect for all your flips and spins.

Versions with special locking mechanism's such as laces or snowboard like tension straps (as pictured) are now available, these make entry easier and provide better support. If you are serious about wakeboarding these are what you want. One disadvantage is that they are only really suitable for one or two shoe sizes - so you better hope your feet dont grow.

Some also mold to your particular foot shape, so it is an excellent excuse to stop your friends using your board and bindings.