My son bought an Oregaon red spotted garter snake at the Columbus reptile expo yesterday. It's an adult male, and we loved the yellow stripe, red dots and its blue belly. It's somewhat darty, but calms down quickly when held.
He just inhaled an f/t pinkie, and I am amazed at how active the snake is. He really seems to want to explore his surroundings. (This also makes it not so easy to take pictures.)
The online descriptions for ideal enclosures for garter snakes varied quite a bit, from what I could tell. What has worked out for you?