I've reused spokes with no ill effects, but there's a couple things to consider:
I've been building my own wheels for 30 years.
These are high quality DT spokes, that I bought new and laced into my own wheels.
I don't abuse wheels, aside from my own not-insubstantial weight (220 lbs.)
I disassembled these wheels and kept the spokes separated by position: left side, right side, inside of flange, outside of flange.

It looks like you're going to this class: http://www.citybikes.coop/about-citybikes/classes/

Frankly, choosing hubs, spokes, and rims is pretty academic. When it comes to wheelbuilding, the true test is whether the wheel is durable and maintenance-free. That comes from building wheels with high, even tension, which comes with time and repetition. IMO, building good wheels is mostly about learning the patience to do it right. Some people get do fine the first time, some people never get it.

If you want to talk wheels, maybe we can meet over coffee when my work project calms down. My "day job" is taking over my life right now- I work at Legacy Emanuel hospital. We're opening the new Randall Children's Hospital this weekend: http://www.legacyhealth.org/rch_body.cfm?id=1045