While I don't have personal experience, I have had animators in my circle, and have watched them animate. They generally employ a range of software for different steps.

I downloaded a software for basic animation a while ago, it's called Stykz. When I did a google search for more like it, I found this article, which includes links to other software I recall seeing in use. I've fallen out of touch with my animator friends over the years, otherwise I would hit them up and get some updated information.