Tiffany, over at Nature Moms, tried out every sippy cup available on the market that was BPA free. She and her children rated each cup whether it was comfortable to hold and whether it had a tendency to spill or leak. This cup by Thermos was the grand winner. This cup is stainless steel and has a soft plastic spout. You can also get it with or without side handles.
$14..49 at Amazon
This version is good for kids a little bit older.
$29.99 at Amazon