Just to let you know. I once tried volunteering for a domestic violence hotline. I have to tell you, it was an awesome experience! Maybe it's not medicall related (i've done a ton of medicall related stuff, so in my case, i don't think adcoms would really care), but it probably taught me a ton more then i ever got volunteering at an ER. ... Why? mostly, it was communication with DV victims.
I agree, go look at voluteer match, or something like that. If nothing else, it will show you what is out there. you probably may even find something like big brother, but also medically related (some places I've seen being like a big sibling for chronically ill kids). Don't be afraid to try something new, also, even if you know you'd love being a big sibling.
but, if you finally go around, and try other stuff, and feel they aren't your thing. do NOT stick with something, just because you think medschools want you to do it.
anyway, most of all. Here's a quick an easy test to tell if something will be worthwhile (if you' re not sure by the description): if they require training(not a TON, make just a few sessions), that is a huge plus. That means you'll be given responsibility. That usually means very good. Also, don't be shy to ask what other volunteers thought of the program.
Sonya