I really like the Contigo mugs/water bottles. You press a button to drink from them (the button is at the neck of the bottle, so you can drink from it one handed). When you release the button, they automatically seal. If you drop it, it seals on the way to the floor. If you knock it over, it doesn't spill because it sealed as soon as you released the button.
The insulated 16 oz mug in Stainless is awesome. My DD (3) just got the Trekker cups and they are coming out with a smaller insulated one in January. The website is gocontigo.com
Target and Meijer sell a few of the Contigo products.