I don't think that it's very important, but it's always nice to have something write something in the ERAS (the residency app) volunteer-wise that you did outside of med school. There is a section for it, and it's probably not good to leave it blank, but I suspect that most programs could care less what you put in it. The only exceptions would be things like the family medicine residency (very non-comepetetive), the program director told me that they like to see community out-reach, preventative medicine type activities on their applicantions. But then again, my school only filled 2 out of their 9 available spots in family medicine this year, so I think that just turning in an application and ranking my school would have gotten you in. On the flip side, if you do too many outside activities, some program directors may interpret that as you not spending enough time in medicine or having too many interests outside of medicine (eg you won't work as hard in their residency program). That's more of rumor I've heard though.
