I would go with an HP ScanJet. Try and get one 
with at least 600 dpi resolution, or 1200dpi if 
you can afford it. I personally use an HP 
Scanjet, but I forget the model number because Im 
not in my dorm room right now... It cost me about 
400 dollars, but the only reason it costs so much 
is because Im an amatuer photographer, and I need 
the speed, rez, and color saturation of 
professional level equipment. But I would say 150 
dollars would buy you a good scanner, fully 
capible of scanning cels. 

By the way, using a digital camera is a really 
bad idea for imaging cels. The rezolution of even 
6,000 dollar pro digital cameras dont even come 
close to the full image rez capability of a color 
scanner. Not to mention, you cant get a good 
color balance on the cel, and trying to get a 
straight on shot of the cel will result in blurry 
edges on the image, due to the differing 
distances from the lens of the camera to the edge 
of the cel, versus the middle of the cel.

Ok, back to studying...
-Mike