There were actually only ever a maximum of around 10,000 Spartiates (Citizens and Soldiers) at any one time, and at least half of these always remained in Sparta to prevent the slaves from revolting. Personally though I almost prefer their political system to the Athenian "Democracy", which left their system far more open to corruption and demagogue rule.
Once I gather up the cash to pre-order I'll probably go Spartan.
I believe the 10,000 Spartan citizens which made up the bulk of their armed forces were called Homoioi - effectively "Men of equal status". They were not involved with manual labour and had the most freedom and power within the Spartan society.
Next comes the Perioikoi - they carried out the majority of tasks revolving around commerce and trade - the Homoioi were forbidden to do this too T__T
Lastly comes the Helots (poor sods). Basically enslaved populations who were tied to the land they worked by the Spartan state.
I think there were also Hypomeiones who were Homoioi who had lost their status within the society - not so sure on that last one though so may need to refresh my memory.
Then again I am recalling this from my Classical Civilisations classes at A level so anyone please correct me if I'm wrong :3