CTCStore offers Amazon Prime members the Acase Splendid 3D TPU Case for iPhone 4 / 4S for $3.25 with free shipping. (Non-members can spend over $25 to qualify for free shipping; otherwise, shipping costs $5.40.) That's $1 less than our January mention and the lowest total price we could find. It features a 3D bulged square surface. Deal expires May 16.

Amazon Prime membership is $79 per year; however, Prime is free for college students for six months, and free for parents and caregivers for three months. (Note that there's currently a wait for the Amazon Mom program.)