If you need stuff to do there are plenty of people who'll accept your help. More specifics will probably get you more attention in the areas you want. For example, are you funding some costumes, or want someone else to fund and you'll do the labor? What types of costumes are you interested in? What are your specific talents? Design? Tailoring?
Just like FallenAngel we're willing to use help if someone is looking to help. Our set-up should be done by Monday and our themed costuming is fairly simple at the moment, being Tiki themed, Hawaiian shirts are cheap. Having a desire to help, you'll find plenty of welcoming people so you need to try to find the ones you'll fit in with best.
Also I have some costumes in mind for myself that I lack the talent and time to make. If you want to help me with some design ideas of how to make some good ideas actually look good, I'd love some assistance.