Here s a great resource for learning Lua, it s aimed towards beginner programmers (doesn t sound like you), but it does a great job at introducing Lua and most of the basic concepts:
Lua for Beginners:
http://lua.gts-stolberg.de/en/index.php?uml=1
That, as well as the "Learning Corona" section of the Ansca docs should be plenty enough to get you up to speed in a very short amount of time:
http://developer.anscamobile.com/resources/docs/
TIP: Start working on a project, or converting an existing app using Corona and you ll learn it blazing fast! That s what I did, and I learned it quickly enough to have one of my games fully converted in about 8 days.