The two sites that helped me the most when I first started were Doug Smith's and this one: http://www.forumancientcoins.com/moonmoth/ancientcoins.html In addition, here's a great site for identifying late Romans, particularly when you can't make out much of the legends: http://www.tesorillo.com/aes/home.htm
Thanks Gao, I'll bookmark those as well and check them out! Taylor, I got it from a coin shop up here in Oregon