Here are the instructions I have, I couldn't figure out where I found them:
Altered paint can
1. Remove the handle from the can. (actually, I didn't do that the first time I made one - it makes it a lot easier in the long run).
2. Cut two pieces of cardstock, patterned paper or fabric 7 1/4 x 10 3/4. This will leave you some overlap at the seams and a small gop at the top and bottom. You can easily split the 7 1/4 measurement in half if you want to use 2 different papers to cover the can.
3. Place a mark about 1 1/2 inches down from the top of your paper and use a 1" circle punch to cut out holes for the handles.
4. Once the paper is cut and the handle holes punched, you can stamp, ink, sew, draw or right on the paper before it is adhered to the can. (okay here's another thing I messed up on my first can. It wasn't a problem, but it's definitely easier to stamp on a flat surface). Any lumpy embellishments can be added to the can after the paper is attached to the can.
5. Adhere your paper to the can.
a. If the paper is lightweight, you can use double sided tape (I like Terrifically Tacky Tape) to attach the paper along the seams. I just run one piece of 1" wise tape up each side of the can, right under the handle.
b. If you're using heavy weight cardstock, or if you want your can to be a bit more durable, you'll need to use Mod Podge or some other decoupage medium. If you use a wet adhesive like Mod Podge, you'll need to prepare the surface of the can before you start. Do this by giving the can a light sanding with medium grit sandpaper. Use a foam brush to apply the paste to the can and then place the paper. Some people like to slather on another coat of Mod Podge over the paper. You can do this tidily or really sloppy, depending on the look you're trying to achieve. Allow some drying time before adding embellishments. ETA 10/12/07: I suggest using some Tape to hold the paper down. I have found that the paper will try to pull away after time when just using mod podge.
6. To create top or bottom borders, or a horizontal stripe around the middle of the can, cut a strip or paper or a ribbon and adhere with double sided tape.
7. To cover the lid of your can, I find the middle-sized CM circle cutter, using the blue blade yields a circle that is just the right size. You can also use a compass set at 2 5/8 inches to yield a circle with 5 1/4" diameter. (Be warned, when I used a compass I had an ugly flashback to geometry class.....). Again, adhere the paper to the top of the can with double sided tape or Mod Podge.
8. Once the surface is dry, you're free to embellish your can as you wish.
9. Replace the handle of the can.
10. Tie ribbons around the handle and decorate the key to hide any mismatched paper along the side of the can (Trust me, no one will notice, but if they do, shame on them).
good luck!
I got my paint cans at Lowes and I think they were under 3.00 !! 
you just got to love Lowe's!
