Derailleurs Shimano 8spd front, Shimano Sora 8spd rear
these are the listed specs on one of the bikesdirect bikes. 64 speeds. Cool. Bet it can climb a tree in low gear.
As for what type of bike you can find for under 500 bucks? I'd go with my favorite brand......used.
Very good nearly new bikes can be had for less than half price. Slightly older ones for a small fraction. I honestly don't ever see myself dropping the money on a new bike. Well, maybe when Obama comes out with a $1000 tax credit on one I might bite.