you're right about the metal bus line, thats actually a much better idea.
those LEDs will be pretty bright at 20mA - so bright you might not want to look at em straight on.
try getting a few values of resistor to try out first - 100ohm, 150ohm, 200ohm, and maybe even a 250ohm. I think you'll find that it will be more pleasant to look at with 200ohm or so, they wont be so piercingly bright (bulbs of this brightness are the ones in LED keychain flashlights and the like. those are pretty bright).
you are right, assuming the forward voltage of that LED is only 1.8V. But for the 3V blue LEDs that he selected, the resistor will need to be 200ohms for 10mA and 100ohms for 20mA.
as far as resistors and switches, radioshack will DEFINITELY be expensive for buying 50 switches. try an online retailer, and try to get both resistors, switches, and wire from the same place to save on shipping, thats usually where they get ya with this stuff.
I use jameco but there are others.
resistors:
CF1/4W201JRC: VARIOUS: Passive Components
switches:
GPB001-R: JAMECO VALUEPRO: Electromechanical
Jameco Electronics - Electronic Components Distributor
the first switch link is the cheapest one i could find there. You are looking for a momentary contact, normally open switch. Just about anything will handle the 5V, in fact the lowest category they have is 12V.
sorry i dont mean to push specific websites, its just more convenient to show one, heh