I agree that all of my hospital volunteer experience (transfer dept and ER) was worthless and a waste of time. I did remedial tasks like filing (ugh) that the medical assitants didn't want to do, although I did get to see some cool stuff.
I think my most valuable experience came with summer jobs, etc, which provide direct patient care and often leadership roles, which I thinkwould be more impressive than, "yeah, i found that i loved wheeling people from their rooms to x-ray, it was so nice to talk to them and get to know them on the elevator ride down and back..."
I was able to take an EMT course during winter break, and ran with my school's EMS team. I bet your loal FD is dying for some volunteer EMTs.
It may be a little harder to become a CNA, but look into your state's regulations regarding assisted living facilities. I was able to take a 2 week course and pass meds on an alzheimers/dementia unit of a residential home (not a nursing home), which I felt was great experience, and put me a notch above the responsiblities of a CNA. Or see if the activities director at a nursing home needs any help - in high school I played checkers with old men, and painted cute littlle-old-ladies' fingernails. They love the attention-half of them are dying for someone to talk to, and I found it more meaningfull than the aforementione filing (ugh).
I also worked as a surgical tech one summer, and got to see a ton of surgeries. Look up job positions on your local hospital's website, there may be summer openings for all kinds of techs.
I also volunteer at a women's homeless shelter, and while it isn't medically related, it is fun, engaging, and makes me feel as though I'm actually making a difference in someone's life. I'm sure there's a soup kitchen, homeless shelter, or habitat-for-humanity project in your area.
In short, follow your interests. There is much more to medicine than hospitals, if you just look hard enough, and most of it will provide more patient care and responsibility, and won't feel like a waste of your time. But then again, I haven't even applied yet, so what do I know. I would have done the stuff I did even if I wasn't applying to med school, and I think that matters more than anything. (see the former disclaimer).