Enjoy your summers in the underclass years while you can. Because you won't get them later. Especially after the 3rd and 4th years (in the new 5 year curriculum), you'll be trying to arrange electives back home and/or studying for the damn USMLE steps. Before that if you were really keen, you could try research... but it's hard to do anything without contacts.
I spend a significant portion of my summers here because the rowing season doesn't end until mid-July. So the first year, I did research here (free, a little bit of grant money). Tne 2nd year, I continued research here (for pay). The 3rd summer, I did electives here (I couldn't work doing electives at home because I was unwilling to pay a lot of money and my homestate wouldn't accept non-final-yr. students even though I tried to bypass that) and did some USMLE study. not much of a summer. My 4th summer, I'm doing more USMLE study, elective in the US, and our year starts on Sept 4th (after this year ends on June 30th) so essentially, again not really much of a summer.
Other people can work having more fun if you do electives abroad (ie. 3rd world or other places)