Hi fun8stuff,
I'll give you 2 answers: 1) the answer I want to give you, 2) the answer you wanna hear.
1) Do whatever you like to do! If you're a cyclist, do the AIDS ride from SF to LA. If you like to work w/kids, there are plenty of opportunities to do that. If you like older ppl, volunteer at a nursing home. If you like to paint, get some blank canvases and paint with them. If you're crazy about research then get a job doing that in your college. I discourage ppl trying to find the "right" thing to do simply to pad their resume.
Some rules of thumb in this vein:
Be creative.
Keep your eyes and ears open for opportunities on/off campus.
Network! It got me the best job in the world (what I'm doing now, running a clinical study)
Take initiative. Create your own job/internship. Approach organizations who are dying to take free intelligent labor.
Bottom line: do what you love and excel at it. Go all out.
There is NO formula for getting into med school. That's what make it so great and difficult at the same time. From my interviews I've met so many cool ppl and they're from all different backgrounds. Don't worry about how your summer plan looks to others. If you are fired up about it, chances are others will be too.
2) One way to look at it is to see what kind of experience you are lacking. Is it:
research experience?
clinical experience?
other community service?
grades? (applies if you're not applying this cycle. If you are, then grades this summer won't matter anyway.)
Use this time to strengthen your application. If you're great all around, good for you. See (1).
cheers,
sunflower79