I've just released the beta version of TryLogic. It's an online propositional logic parser inspired by TryHaskell and TryRuby.

The objective is to help High School and Junior students with their logic exercises. All formula evaluators I've found are old, ugly and/or too complex for newbies.

There's still no "help" and other learning stuff, but it's open source, so I hope other people interested in helping will contribute at Github https://github.com/joaomilho/trylogic. (No, there are no quantifiers yet)