Mould usually grows when water does not dry properly on the ends of shower curtains. To combat this problem, you can sew a ring onto the corner of the curtain and mount a hook inside your shower area. This allows you to hang the ring to facilitate proper drainage.
Instructables user mole1 found that by sewing a ring onto the curtain and attaching an adhesive hook that any excess water on the surface of the curtain dripped toward the drain. You should be able to find the proper shower curtain ring for a few bucks and spend about the same amount for an adhesive hook. Just attach the ring on the hook after you get out of your shower, and you'll have much less water retained on the curtain. However, keep in mind you still need to wash your shower curtain once or twice a year.
Have a mould free shower curtain in your bathtub [Instructables]