Some are adorable and others are highly disturbing. There's a lot more of dress/costumes that look like the Skittles one but I don't really consider these costumes (I would wear this dress in public on a non-Halloween day) so I only picked my favorite. Some of these are homemade but most of them are store bought.
*the one covered in white with a brown comforter is supposed to be a cannoli
The photos above are the work of fashion and costume designer JoEllen Elam. Her website: www.firefly-path.net contains multiple galleries of her many collections including Musing Mermaid, Dragoon Warrior and Masquerade Fairies (select images shown above). JoEllen also does commission work for accessories, wings and additional costumes.
A coworker of mine directed me to this site. The Theatre Development Fund (TDF) rents out costumes used in professional shows for special events and smaller productions. They look pretty cool - not like I'm putting on a show any time soon. But if you're in Manhattan it may be worth a look around. Their address is: TDF Costume Collection, 601 West 26th Street, Suite 325, NY NY.