I just saw a big rack of 65W compact flourescent floodlight fixtures at wal-mart for $11 each. I've seen them at hardware stores for $40 (bulbs alone for $12), but these guys are super cheap. They're 6500k too.
I've previously used T-8s for inexpensive DIY fixtures, but these new CF lamps appear to be a cheaper, lighter and smaller option. Set one on a 10G with a glass top and you'd be ready to go in minutes.