I only read about half of the posts, so these were probably said but as a mechanic this is what I check for when there is a mysterious creak... make sure bottom bracket is tight, if possible, remove and re grease threads, tighten crank arms, remove and re grease pedal threads, make sure the pedals themselves are tights, tighten crank arm bolts, if need be remove and re grease those threads. If all that fails then you're problem isn't in that area. Loose spokes will most definitely make a creaking sound, and you should definitely get them professionally tensioned and trued.

I am all for people learning how to work on their bikes. They are simple machines and don't take too much skill to work on. However, some parts do take very specific tools, and if you don't have them, don't try to work on those parts. You will most likely end up ruining the piece and then when you can't get it fixed you'll take it to a shop where they will no longer be able to work on it, and you'll have to buy a new part..it happens way too often.

side note- A buddy of mine tried remove his crank arms with a crow bar. He got off the drive side fine, but the non-drive side snapped in half and went through his face below his mouth. A bunch of stitches later, he now owns a crank puller.