Dismayed by the cost of the shower curtains that I liked in stores ($60CDN!!!), I decided to make my own:http://mydogmeg.net/images/projects/shower/shower_300x400.jpg
About 2-1/3 yards/2m each of at least two fabrics, 45"/115cm wide
1 package of 12 grommets
1 vinyl shower curtain liner
To determine how much fabric you need, buy the vinyl liner first. The average size seems to be about 70" long by 72" wide; you will want enough fabric that you can piece together a sheet 11" longer and 5" wider than your liner so that you have enough for hemming. Also, a note about grommets: make sure that you buy grommets with holes that are larger than your shower curtain hooks!
Wash and dry the fabric. The curtain is likely going to get wet from time to time, and at least it will be exposed to high humidity while in use, so it should be a fairly resilient fabric - poly/cotton blends work well as they usually don't require much ironing (unless you're the type of person who likes ironing things like shower curtains and sheets, in which case, knock yourself out with 100% cotton!).
Rip the fabric longwise into strips of random width. Since you'll be sewing with a 1/2" seam allowance, the narrowest strip should be at least 3"; my widest was about 14". The nice thing about ripping is that they should all be straight, which makes the next step easier: sew the strips together on the long edges, mixing up the colours and widths however you please, until you have a piece 11" longer than your liner. Cut the width to 5" wider than your liner. Press all the seams toward the bottom of your shower curtain.
For the top hem, fold the top 3" toward the wrong side of the fabric, and then fold 3" down again, over the first fold - this will give you three layers of fabric, and no raw edges at the top or bottom. Sew this down about 3/8" from the top of the curtain and again about 3/8" from the bottom of the folded edge. For the bottom hem, fold 2" toward the wrong side of the fabric and then over again, and sew down the same way. For the side hems, fold 1" toward the wrong side of the fabric, and then over again. Your hemmed curtain will be about an inch longer and wider than the liner.
Lay the curtain right-side down on the floor, and place the vinyl liner on top of it so that the top edges are flush and the liner is centered width-wise. Make a mark through each of the holes in the liner, onto the curtain fabric. Follow the instructions on your grommet kit to put the grommets in (they usually come with a little tool and you have to hammer them).
That's about it. The total cost of my curtain, including the vinyl liner, was $22CDN, thanks in part to a great deal on the fabric ($2.42/metre!). It took about 2 hours to complete.