What is a good memory card for a nikon D 80 and flash for an event?

I have been asked to take pics for a party that someobdy I know is having. He is going to buy the memory card,and possibly the flash but i'm not 100% sure what to get. My 4gb card can hold around 700-800 pics on the highest quality setting. I would really rather not bring my laptop, so i'd like a larger card. The one I have is a san disk pro. I'm not sure how much I am going to shoot that night, and would rather not have to bring my laptop as the even will be at a club.

I'm not sure if I am going to purchase the flash myself, or make him pay for it. So I also need the name (or names) of some good affordable external flash's since the club will probably be fairly dark, and i'd like good quality photo's.

Thanks in advance for your help