Idea 1: Sprinkled throughout Atiyah McDonald are over a dozen exercises concerning the structure of $Spec$.  Undoubtedly a great many of your students are taking commutative algebra because they are interested in algebraic geometry, and this would be particularly useful for them.  The challenge would be to come up with a "punchline" which ties the project together.

Idea 2: Those students who are not taking commutative algebra primarily to learn algebraic geometry are probably interested in number theory.  A nice project might be to prove from scratch that every prime in the ring of integers of a number field splits as the product of primes in the ring of integers of any finite algebraic extension.  If I recall correctly, this only uses basic facts about ideals and modules over Dedikind rings.  You might even be able to discuss a little bit of basic ramification theory.