I've fed all mine baby ratsnakes, baby corns, storeria, garters, and the like.
I do have one piece of (albeit controversial) advice, do NOT feed them a ringneck.
I've heard some people say they fed theirs ringnecks with no problem, but I've heard just as many say that ringnecks were toxic to them.
The reason I tend to agree with the 'toxic to' crowd is that a friend kept an eastern coral for 13 years. when it did die, it was just hours after consuming a ringneck. ....
one or the other may be correct, but my thinking is.. why risk it?
oh, one other thing.. the absolutely LOVE baby eastern kingsnakes. baby kings are like candy to them.