Well, in my humble opinion, for 2D animation there is Flash, Toon Boom Studio, and pulling up slowly in third is Anime Studio Pro (formerly Moho). At least in the low to moderate price range.
If you are asking with respect to employment, most studios look for raw talent, as the software, which is sometimes proprietary, can be taught.
Thoughts on 3D anyone?
I believe Maya is in high demand for 3D animation. 3D Studio Max is also good to know. However, these programs are very expensive. If you are a student I would try to purchase them with an academic discount. http://area.autodesk.com/