I found a great deal at Ross (Dress for Less) for some brown full length window curtains. They were $8 for 2 panels. I don't think I could have purchased fabric for that price.
I cut the curtains the length I needed and hemmed the bottom. I then used the extra fabric for a second layer to really block the light (since only one layer wasn't enough to block out enough light).
The trick was this: I turned the extra fabric on the side (i.e. the new top and bottom to the liner curtain used to be the side hem before the curtain was chopped off) and threaded string through. The curtain rod I had didn't leave space for another curtain rod behind it so I rigged up a string system - fancy I know. I attached the string to each end of the curtain rods and then loped it around a nail hammered in the middle of the window.
I realize this isn't the most beautiful system, but it works great. We'll be moving in a year and I don't know what our new windows will look like. Until then, I have a beautifully finished curtain and a great liner for blocking out more light!!
p.s. I left a little bit of light peak out of the bottom so my son wasn't in total darkness :) His curtains are now done and he's sleeping in until 7:30-8am! Perfect!