CodeRunner is a Mac app that lets you:

Edit and run code in AppleScript, C, C++, Java, JavaScript (Node.js), Objective-C, Perl, PHP, Python, Ruby, Shell or any other language you might have installed on your system.

This could be really useful for programming teachers — one of the big headaches we always have in the first lesson was making sure things were set up properly. There was a time we tried teaching C++, and found out that the computers’ permission settings disallowed running of any shell programs, so we sang songs and dreamed of correcting missing semi-colons. Ah, fun times.