Bike repair help from a good neighbor?

I bought a used bike on the cheap last week - because it's in my nature, I started taking it apart to see if I couldn't clean it up a bit and see how it worked - naturally, being a doofus who doesn't think too far ahead, I failed to take pictures or worry about how I was going to put it back together.

It's certainly cleaner now, but I can't, for the life of me, figure out the correct way to get the derailleur functioning or the gears to shift (the chain has no tension). Plus, which is always fun, I've ended up with an extra screw...

Is there anyone in the 'hood who would be willing to work with me, either in person or via email, to try to get it working? There must be plenty of bike enthusiasts around here who are just aching to showcase their talents, I'm guessing it wouldn't be difficult to fix for someone who knows how, I'm just not that guy. Plus, I'm too cheap/too curious as to how it actually works to take it to a shop just yet.