I'm female and I commute May - August. I agree with a lot of the advice already posted.

- Rolling my clothes works for me. I put my clothes in a plastic grocery bag inside my backpack if I take my road bike (keeps them from getting sweaty if I get too hot on the ride), or I put the plastic bag in panniers if I ride my hybrid.
- I have found that skirts and casual dresses actually fare better than pants when rolled up.
- I have access to showers at work, but keep a towel, makeup and toiletries at my desk to make things easier.
- *MOST IMPORTANT* Keep spare undergarments in your desk. My spares have saved me from going "commando" on several occasions when I forgot to pack undies the night before.