Corn snakes are wonderful. Docile, easy to care for, great eaters, and they come in all kinds of colors. I have 3 corn snakes (and have cared for more than that) and absolutely love them!
Ball pythons are good snakes for the right person. Personally, I'm not a big fan... They're boring, and many of them have troubles eating consistently if their living conditions aren't perfect or if they're handled too much. Mind, there are ball pythons that are active and eat great no matter what... They just don't seem to be the norm!
Anyway, that aside, ball pythons are docile, very laid back (as in, they usually just sit there when you handle them). Their care isn't as easy as a corn snake, but it's pretty straight forward. They're bulkier, which makes them a better fit for some smaller kids who might be too rough on a smaller/thinner snake like a Corn.
Balls and Corns are the two most common "beginner" snakes, but there are others to consider. Rosy Boas are GREAT snakes. They're docile and laid back when out of the cage, but relatively active in the cage (not always hiding), they're easy to care for, eat like pigs (sometimes to a fault--one of mine is convinced humans are food... but not all are like that), and don't get very big--generally not bigger than 2-3 feet. But, for their short length, they aren't thin and delicate--they have a nice, solid girth to them.
This is one of my Rosies, a Whitewater:
To give you an idea of size, here she is wrapped around my hand last month... Yes, she's trying to eat my thumb, LOL. Rest assured, not all Rosies are like her. She's a little over-enthusiastic about food. Many rosies are great to handle, especially if you start with a younger snake and get it accustomed to being handled, so it doesn't start thinking everything fleshy is edible.
Other snakes to consider include Milk snakes, King snakes, Sand boas, Antaresia (children's, spotted, etc) pythons, even some of the larger, less hyper-active Garter snake species are great pets, and can be great beginner snakes.
Some resources...
Corn snake forum:
http://cornsnakes.com
Ball python forum (they have a
care sheet to look at--I'm just too lazy to link directly to it, lol):
http://ball-pythons.net
Rosy boa
care sheet:
http://www.vmsherp.com/CarePages/CareRosyBoa.htm
Sand Boa Page:
http://www.kingsnake.com/sandboa/sandboa.html
Children's Python care sheet (Spotted pythons have about the same care, they just get a bit bigger):
http://www.tinypythons.com/caresheet_childreni.asp
Garter snake forum (again, they have a care sheet, too):
http://www.thamnophis.com/
I would link a King and Milk snake care sheet, but there are so many subspecies of each that no care sheet can cover them all. If you decide you like a particular king or milk, you can do a search for a species specific care sheet to find the most accurate information. (For what it's worth, Mexican Black Kingsnakes and Black Milks are stunning and awesome. Thayeri/"Variable" King snakes live up to their name--they come in dozens, if not hundreds, of different color and pattern variations, plus they're great pets. Cali Kings are one of the most common, and also great snakes. Honduran milks are docile, big, and come in all kinds of colors... There is a lot of variety in the genus
Lampropeltis!)