I worked with student worker alliance program (SWAP) on campus for service learning credit in spanish two years in a row. This group is great because it pairs you up with a migrant worker to teach them English. In this process, not only do you do a lot of good and learn how to teach and communicate more effectively, it also helps you practice another language. This is good for spanish and other languages as well. Other than that, get involved with groups that work with low income communities or other ethnic communities locally. One student group would be CU going local.

SWAP is a great one that I know of

SWAP is not only good but it's the only one i know of on campus