Pink Sports Yoga Exercise Jogging Running Armband Arm Strap for iPhone iPod
I picked up this armband for my iphone 3gs, mostly because its pink.  It works well enough, might be too big but again, it works.  I have to take the cover off of my iphone for it to slide in and the part that holds the phone came away from the band on a corner, so its not well made.  For the price though, this will work.