How many spaceman minifigure variations exist?
A full list of space related minifigures can be found on Bricklink here as well as under the Town theme. If you count fantasy themes there are also many astronaut minifigures under Alien Conquest, Blacktron, Life on Mars, Mars Mission, Space Police, etc...

There is also the Spaceman from the 1st Collectible Minifigure series.