I would encourage anybody interested to try out the site's quiz. It starts out easily enough but eventually becomes extremely challenging.

I also really like the community submitted regexes. But, on that note, what's to prevent someone from submitting all of the quiz solutions to the 'community'? Are the submissions occasionally moderated?

I have appreciated this website for a while now. For those who don't know, Lindrian is also often active on #regex on freenode IRC, which is a great place to get feedback on regexes. (Or to just be told many times not to use regexes to parse HTML.)