This one's for the real code geeks.
Point and click RE generator
It's pretty slick, but not perfect. You can't alter the groupings it parses out (e.g. I gave it the string auto-224 and it wouldn't let me treat that as a single unit, it broke it down to auto, -, and 224). Plus, the ideal tool would let you enter 2 (or more) strings and generate an RE that successfully matches both. Or perhaps enter a bunch of strings and generate one that matches some, but excludes others. THAT would be great.
But this tool still has its charm. At the very least it's a quick way to see some valid REs in action, I'll definitely be bookmarking it.