I followed Ana's instructions completely, so I'd check out her plan. But, I'll go ahead and give you a play-by-play here.
Time Commitment: 1 hour
Cost: around $10 (enough material for three 2 1/2 foot shelves)
Tools: (I got all of mine at Lowe's)
2 1x4's at 8 feet long
1 1x2 furring strip
2 in finishing nails
2 in wood screws
Stain or paint
1. Measure out how long you want your shelves to be on the 1x4s. I chose 2 1/2 foot shelves, so I marked it with a square and cut. I'd recommend marking and cutting separately for each piece. As you won't cut exactly on the line every time, this will make sure all the pieces are as close to 2 1/2 feet as possible.
Note: Wear safety googles! (Or sunglasses if you don't have safety goggles...) Unless, you want wood shavings in your eyes, of course. (Really not fun)
Then we just screwed them into the wall! (Do not try to use anything but screws directly into the wall. It will not work. Not like we tried...duh.)
And Happy Halloween!