Mountain-Grown Silver Halide Crystals, or, The best part of waking up is developer in your cup.

So it turns out you can make your own B&W film developer using coffee, sodium carbonate (soda ash or washing soda), and water. I don't know that I'm up for trying this out just yet, but it sure seems like a good idea in a pinch, and would likely work out much cheaper than a packet of Dektol.

There's even a group on Flickr dedicated to homemade film chemistry with enough solid results to make this look viable.