IU's VOSH goes to Guanajuato, Mexico anually. We go next week actually. We generally take 5 first years, 10 second years, and 15 third years. Then theres about 10 docs and fourth years that go. We set up a temporary "assembly line" clinic at the convention center and see about 2800 patients in 4.5 days of work. We have to do fundraisers and other activities to earn points to go on the trip. We end up paying $350-450 out of pocket. Most everyone who wants to go gets to. IU also has a clinic in Guanajuato, so 12 intern per year get to do a 3 month rotation there. I go this summer, yay! I should be pretty good at spanish by the time I get back.
http://www.opt.indiana.edu/clinics/centers/mexico/mex_indx.htm
IU also has a strong FCO chapter (the original chapter?) that organizes trips to Honduras. They tend to go during the summer or after Christmas. They usually request money from their church groups. I think its usually about $1200 minus whatever money you can fundraise.