Considered peaceful for cichlids are, German Blue rams, bolivian rams, keyholes, apistogrammas, these are the smaller variety of cichlids, as you start to go into the larger varities, angels, acaras, geos, terrors, severums, oscars (to name a very few) they more aggressive they become.
Its hard to recommend which would be best with other fish, without knowing what other fish we are talking about, however the smaller variety I mentioned are considered peaceful enough to co-exist with a wide range of 'community' fish. Tank size is also dependent on the level of aggressive some fish will display, obviously the larger the tank the more choice you have and the less aggressive some of these fish will show as they have more area to call their own.