Like Tiffany suggested, garter snakes are great. They don't get huge or heavy, they are active in the day time and like most colubrids, some seem to be engaging with their humans. Although I'd have to say my personal favorite is the western hognose. They are also a smaller snake, eat very regularly (especially females from my experience), and are also active in the day time.

Both do well with handling if you handle them enough.