iArmbands iPhone / iPhone 3g S SlimLine armband - For 4gb, 8gb, 16gb, & 32gb models - 3g, 2g, 1g
Very happy with this sports band for my iPhone.  I run 3-5 times a week and use my iPhone to track my activity.  The arm band is very comfortable and the plastic front allows for easy use of the controls.  Great deal for the dollars.