So I just went shopping for some supplies to make my grow rack look a little more professional (and keep more light from spilling out into the room -- my girlfriend who is preparing for the MCATs uses this room to study).
I went from this:
...my cat is a camera hog
I used 1/32" thick sheets of opaque gray plastic to cover each shelf, the top, and the back of the rack. I used an old black towel to cover the sides (to allow for more air flow), and a cheap set of vinyl miniblinds to cover the front. I'm pretty happy with it!