ghacks.net has posted a tutorial on how to use OpenOffice to create flash cards. The tutorial does require downloading the OpenCard extension, which is available for free. From the article:
The OpenOffice Impress OpenCards extension allows you to take a bare-bones presentation and use each slide as a flash card. Not only is a great tool for learning, it’s not killing trees AND a stack of files on your PC is going to take up less room than a stack of paper flash cards.