If you need more specific placement (in a grid, sphere, cylinder, spiral, line,...)
you can also do it with layer placement iExpressions:
http://mamoworld.com/after-effects-expressions?filter=tid-19

They make it also easy to transition from random positions into such shapes or add some wiggle to the placement.

For simple random placement in a specific range, there is the
http://mamoworld.com/after-effects-expression/distribute-3d-random
which should do something similar to the 3D Layer Distributor, just with an expression instead of a script.

Cheers,
Mathias