I used to use an Excel spreadsheet. I've heard good things about Degei, but it's not Mac compatible.

I use iHerp now. My computer is a laptop so I just carry it in the snake room and enter the information as I go through each snake.

I didn't like iHerp at first, but I've gotten used to it. The one thing I wish I could do is download an animal's into a spreadsheet on my hard drive so it's easier to print.