You don't need very many parts, but you don't need too little, either. Here's a list of what I used:
1) Two identical motors (I used the motors in two bug vacuums, the toy kind, but any 6-v motors should work) here, this should work: http://www.radioshack.com/product/index.jsp?productId=2914699
basically, two of the same motors
2) O.k., this is the hardest part to find. You need (in my case) two centrifugal fans (i don't know if i spelled that right). Those are the swirly kind. If you took apart the bug vacuums, the fans come with it. I used those. Any hand vacuum has one, or almost anything that sucks air. It seems to be hard to find a small one. If not, any computer fan should work, and you won't need two identical motors if it already has one.
3) Battery holders for your dual motors. (Or single computer fan) Again, make sure the holders hold the battery (or batteries) your motors need. I used a 4- AA battery holder with a switch built into it from here: http://www.radioshack.com/product/index.jsp?productId=2062253
for my two motors.
4) another motor, doesn't matter exactly, but I used a high-speed, powerful 18 v battery from radioshack: http://www.radioshack.com/product/index.jsp?productId=2102827&tab=summary
5) Now you need to find a fan that will fit on the end of the last motor. If the hole is too small, you could probably drill the hole very slightly bigger. If it's too big, I guess you could glue it.
now, here are two links where you don't have to worry about the fan fitting or not: http://www.sciencestuff.com/prod/P-m/0812
(for the motor) http://www.sciencestuff.com/prod/P-m/0823
and here for the fan
6) Battery holders for the single motor, in my case, two 9-v battery holders. As long as the holders hold the battery ( or batteries ) your motor needs.
7) a switch (preferably a push-on push-off switch, but any will work) If your battery holder doesn't have a switch built in, you need another one. Any kind.
8) wire (any gauge)
9) some much thicker, stronger wire, not for conducting electricity, but the wire mounts for the motors. (I used the straight portions of orchid-hanging wire) And make sure that it's not so thick you can't bend it.
10) all the batteries for your motors
11) a large foam meat tray or turkey roaster (like a big, deep metal pot, but thinner and square) and at least 13" by 9.75" ( 33 cm. by 24.5 cm) basically, the larger the better.
12) Plastic, like garbage bag or shopping bag plastic - not way too thick.
13) you also need some other glue, but not so powerful that you can't take it off or remove later, in case you make a mistake. I used hot glue.
14) you probably also want something to cut and strip wire.
15) this is optional. A hot glue gun.
160 something to cut the meat tray or turkey roaster
17) lastly, a tiny bit of cardboard and some glue, or, even better, a small screw and a matching bolt instead of glue
Everything will get clearer as we go along. (maybe) It's really not that much.