you want something that'll show that you've experienced the medical field...either volunteering in a medical setting or shadowing, probably. other than that, do whatever you want with your free time. i took dance classes and volunteered with disabled children. anything that shows dedication and makes you look unique is a good idea. but most importantly, do what you like.
You've been on the forums since november 2005, are you really asking this question? I don't know how you tell someone who has been on here for almost a year to "lurk more", but lurk more. That is, spend more time reading, searching etc before posting silly threads.