I WANT TO SELL A USED MAC?

i want to sell my mac to get a better one, i know i wont get all the money i need, but i want to get the best deal. So its a fifteen inch macbook pro....its battery capacity is at 94% of the original, ive had it for a year and it has 250 gb of storage. As for the software, its a 10.5.8, 2.53 GHz Intel Core 2 Duo and 4 gb 1067 MHz DDR3 (memory) and the startup disk is macintosh HD. so yeah, it also has microsoft office 2008, does anyone know a good site or something where i can find a good price to sell this mac. Also, if i had office 2010 and iLife '11, how much would the price go up? THANK YOU