Places to sell books I no onger want in NYC (?)?

Hello! I am nineteen years old, I live at home with my parents and I am not employed right now ( I have a friend who told me about a spot she may have for me but it's not open until ending of March beginning of April). I need a certain amount of money and I don't like asking my parents since I know they already do enough for me so I've been gathering around things I think I am able to get some money from, like ipods and such...but one of the things I have the most of is books! I sat on my bed and I felt like the answer was right in front of me the whole time, a bookshelf full of books I don't even touch! I live in New York in the Bronx and I'm trying to see if anyone knows of a place where I can get something out of the books I have, bronx, manhattan etc.... Do you know of a place? .... I have different sort of books, science fiction, childrens books, spanish books, etc...