Shooting dancers indoors is in the same category as indoor (low-light) sports. For zooms, this normally requires an expensive f/2.8 lens, or some of the f/1.x prime lenses, to let in as much light as possible. And even then you will need to use high ISO to get the shutter speeds needed to freeze the action.
However, there is always the slim chance that your stages are actually well lighted.
Outdoors, or otherwise in good light, just about any lens will work for you to a certain extent. If you need something longer than the 18-55mm, the 70-300mm VR is a good option for the outdoors stuff.
---------+---------+---------+---------+---------+ Joseph K Seattle, WA, USA