Regular Expressions are perhaps my weakest point with regards to programming.
I realize that they are just little sub-dialects that I need to learn the rules of but I've never had a project which required me to take the time to write extensive regular expressions.
On the rare occasion that I do need to use a regular expression I find tools like this to be invaluable.
This tool looks particularly nice.
Community Forum section, online quiz, even IRC placed right within the page!
My favorite feature is definitely the ability to share a regular expression you've created via a link.
Nice work! (also I just followed https://twitter.com/regex101)