I built a decidedly un-traditional atlatl a couple of years ago, when I was more involved in knife-throwing. A lot of the throwing pages had links to other "hurled" weapons, and I decided to make my own.
I carved the thrower itself from a piece of lumber, and made darts from those 6' vinyl-covered aluminum plant stakes you can pick up at any hardware store. Weighted the head end with wrapped wire solder for balance and made the fletching from....Duct tape!
I have not had much time to refine the thing, but it is great fun, and you can indeed get some impressive distances. There are quite a lot of pages on the subject, ranging from commercially-made items, suppliers of traditional materials, and so forth.
Our Anthropology department had an atlatl "event" a couple of years ago, with all the students making their own and trying to spear a cardboard-box "mastodon".