You can probably get away with safe handling if you wait a solid 24 hours, and the meal the snake ate was not particularly large. It's safest to give the snake a good 2 full days to digest, though, especially if the meal was larger than usual, or if the snake is stressed for any reason, or if his temps have been cooler than normal. Really, it's up to you and how careful you want to be.

EDIT: I always wait a full 48 hours, regardless.