I've always known I'd be better off if I knew how to write regular expressions, but for some reason I never had the patience to teach myself through web searches and online manuals.
Thankfully I just came across RegexOne, a site with interactive tutorials and practical examples using regular expressions. Now I finally know how to write simple regular expressions and know enough to figure out more complex regular expressions when the need arises.
I really like sites that teach with real-time feedback. RegexOne's teaching model is great.