Your best bet is to go through MySims3Blog and Sims3Updates and sort through the female clothes post by post. It's a little bit easier on Sims3Updates, because you can view several "posts" of content at once, and the categories for clothing are more specific. Sims3Updates doesn't always post everything, though, so there's a chance it might not be on there at all.
I'm not sure where that specific dress is from - but I know of many similar dresses. This particular dress looks kind of borked and I wonder what it will look like in game. I know that even with some EA dresses, the hands clip a little - but the clipping here is really bad.
This dress by Anubis has a frilly bottom on the skirt, and can be CASTed to have the polka dot pattern:
Simlicious made a nice flared-skirt dress here:
i-like-teh-sims also uploaded an edited a store dress that has a pretty flared bottom here: