Oh man I think I've always been big into mythology. When I was little and in class the teacher read bits of Edith Hamilton's Greek mythology book to us one afternoon. After that the interest sort of grew. In highschool the Odyssey was freaking fantastic. So all through college I picked up various classical mythology classes (one of them I swear the teacher was smoking something---talking about how dragons can't talk to people and choose to talk to cats I dunno WTF). Anyway, read the Odyssey again and (drumroll) Fagles' Iliad . That teacher had such an enthusiam over Achilles and I think that stuck in the back of my mind. So in picking him up that had a hand in his character.
As far as the Robin Hood myths I think that started as a wee little kid who fell in love with the Disney movie and every other version of it thereafter (because Robin is awesome that way). I even had a set of bow and arrows I target practiced with because my parents were awesome and bought it for my birthday one year.
Those were really my biggest interests that are around that influenced some of the characters I picked up.