as pointed out the spartans actually took the babies outside. they left them in the hills around sparta, believing that if the gods willed it, they would survive. some would, but not by themselves - obviously, as the odd one would be found by the local farmers - who weren't given the privilige of being "spartans" as they were just commoners, rather than mentally-unstable-genetically-screwed-inbreds.
read books by Valerio Massimo Manfredi - especially "Spartan" - they are fairly well based on historical research but with enough fiction to make them interesting....
oh yeah - on topic - "Excaliber" by John Boorman