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Software suitable for animation production is available for Mac OS X.
See the iStopMotion site for more information - email them for Education pricing (current web site price $US 39.95 for a single copy)
The Kudlian software"I Can Animate" is well worth a look as it allows you to draw on the frames as well as using stop motion techniques.
Another alternative that works with Mac OS9 and OSX is Framethief - see http://www.framethief.com