It would be awesome if you could share some cool Regexes that you use more often than not.

The one that I keep constantly bumping into, is the one for validating emails.

function validateEmail(email) {
    var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    return re.test(email);
}

Excited for the answers; more so to update my stash of Regexes. :)