This is a whole long list of patterns and tutorials. I didn’t do much research, so you might know a better one that I didn’t find. And you could always use a short dress tutorial and just lengthen it. There are lots of possibilities!
For my dress I used a pattern that sadly isn’t available. There is a similar free shirt pattern on ICandy Handmade which you can use for the top and shorten it, and then add a flared skirt.
If you want to pin individual pictures from this page to remember the tutorial, please click over to the sites they came from. (Give them the credit for the hard work they did!)