I've been telling people instant coffee will rot yer gut for years now....

This link on Photojojo is where you will find complete instructions.
quoted text:
"Seriously, Coffee?!

Okay, first things first: using coffee to develop film is not something Ansel Adams would do. But it works, it gives your film a distinctive look, and it has a certain MacGuyver-ish flair. Think of it like using a plastic camera- it’s more about having fun than getting technically flawless results.

With most film types, the results will be more contrasty and grainy than regular developer. If you do this with color film (negatives or transparencies), you’ll end up with black-and-white negatives.

Here’s the thing, though: different films will have different results. Some will develop perfectly in 12 minutes, others will take up to 20 minutes. Shoot a test roll of your favorite film, develop it for 12 minutes and see how it turns out. If it’s too thin, it needs more time. If the negatives come out opaque, it needs less time."