Simplicity has recently come out with a couple of patterns, but I don't like them that much and people have reported that the instructions are pretty difficult to follow.

I have a bunch of information on my own web site about sewing dresses, look at http://www.dancesportimage.com

I usually start from a dress pattern that I like and just make the skirts fuller, or (believe it or not), start from a one-piece bathing suit pattern that I like and graft a full skirt on to it. I like working with Kwik*Sew brand patterns for this sort of thing. I've also had good success starting from Vogue and McCall's evening gown patterns.