One of the few things I’ve been missing since moving to OS X fulltime was a decent interactive regex builder app.  The one in Eclipse is great, but Eclipse is about as anti-Mac as it gets.  Others that I’ve used such as regex buddy and regular expression editor don’t run on the Mac.

Well here’s a widget that does the trick quite well, though interactive highlighting of the target string would be even better.

UPDATE: thanks for mentioning Reggy, this is the one I use regularly now, check it out: