A little while ago, Nigel Young posted this very question to his blog. And to be frank, I found the replies (or lack thereof!) to be underwhelming.
I mentioned VideoScribe, PowToon and Xtranormal, all of which I have dabbled with, while another fellow recommended Anime Studio among a few others.
Given the potential for animation to support workplace L&D, I think Nigel’s question is worth re-asking:
What’s the best tool for creating animations?