The Kodak Smile is one of the best cheap cameras, and one of the better instant cameras, too. Simple but effective, the Kodak Smile prints out your images on Zink paper; we didn't like the quality as much as other instant cameras, but the Smile's were good for the price.
We liked the Smile's simple slide-to-open mechanism, though it takes a few seconds longer than most other instant cameras to ready itself for the first shot. However, the Kodak Smile also lets you store images on a microSD card, and unlike other instant cameras, the Smile doesn't force you to print out every photo you take. Considering photo paper isn't the cheapest, this will save you a lot of money in printing costs if you have a happy trigger finger.