Are really easy to make!
Here's a great tutorial on making your own shower curtain. You can really add lots of punch with a new shower curtain, and have one that fits your personal decor--like matching your bathroom paint like I did!
I used inexpensive fabric from Walmart. Being about 42 inches wide, I made a very simple shower curtain of twice that width. I also am finishing the bottom with a ruffle of a different but go-together fabric. I have used buttonholes at the top for the shower curtain rings.
I may do a bit more to the shower curtain eventually--the above tutorial has some great ideas!