Homosexuality was definitely widespread in the Greek world and very accepted, particularly in the military - see Sacred Band of Thebes for an example of it.
http://en.wikipedia.org/wiki/Sacred_Band_of_ThebesAlthough I have little hard evidence to cite off the top of my head, and its controversial, this is one of my major beliefs for why homosexuality is frowned upon in modern western religion - young men, banded together in pair-bondings were a source of constant irritation to the ruling classes and would frequently overthrow governments they believed to be corrupt.
In Greece, there was a ritualized form of 'abduction' where an older male and his friends would take a young boy from his house (with his fathers permission), and the boy would become a sort adored lover - some authors and historians say that this was platonic and unconsummated love, some say otherwise, and again, it seems to vary depending on the beliefs of the one writing it. The Romans, whose ideas on love were more about domination and control, found this kind of love abhorrent because they did not wish to see their heirs emasculated in any way, and slowly began to push it aside - nevertheless, it survives even to this current day in Greek Fraternities in a less sexual form called 'hazing' - something a lot of alcoholic jocks and people who call each other "brah'" would no doubt be horrified to learn. Ideas on polygamy were also a lot more relaxed during the Greek times as well, but our modern beliefs on monogamy were encouraged by Romans as well - it ties in with the need for more Rome-born citizen-soldiers the military demanded.
Rome continues to influence our beliefs even today, though none of us really realize it.
Similarly, as an addition to Code13's mentioning of Geisha, in many stories male samurai would have a young boy following them around as an apprentice/page, and also lover - Miyamoto Musashi had one in the stories about him, for example. Since Japan's introduction to the global community this has been pushed aside and downplayed, sometimes with a bit of shame, but the entire theater culture and military system was rife with it, as it encouraged loyalty to ones lord and comrades in the former, and narcissism and glorifying the male form in the latter.
This is all why we (as a collective whole) in the west are so uncomfortable with the idea of homosexuality in the military - it actually has a very long tradition in many cultures, was widely accepted, and very useful to military discipline, honor and loyalty, something modern society has trouble accepting in any way, shape or form. We live in the shadow of former religious rule, and that engendered widespread homophobia in society.