http://takebackhalloween.org/category/costu…Take Back Halloween: A costume guide for women with imagination.

This site doesn't sell anything. It's a resource guide. And I think it's pretty amazing. You can read their about page for the full scoop on what they're trying to do:

What we mean by “taking it back”

We love Halloween. We really love Halloween. We think it’s cool that there’s one day a year when people can dress up as anything they want. What we don’t think is cool is that increasingly women are only supposed to dress up as one thing: “Sexy _____” (fill in the blank). Sexy Nurse, Sexy Cowgirl, Sexy whatever. This cartoon by Andy Marlette sums it up pretty well:

There’s nothing wrong with sexy (for adults), and if you want to go that route, fine. Have fun! We just want there to be other options as well.

There's even guidance on a Jezebel costume!