If you're going to do presentations (which you will be required to do many) powerpoint is a good thing to learn (takes about 5 minutes to learn). If you're going to do research, excel or some other data-tracking program might be a nice thing to know. But you'll likely be employing some undergraduate student to do your dirty work anyways.
Otherwise you don't need to know anything. PDAs and Pocket PCs are becoming necessary to have, but not till your 3rd and 4th year. Not just for the pocket reference, but more and more hospitals are putting the patient data on the intranet for you to pull up on your palm instead of using a chart. I'm getting one this summer, I start my third year in August.