Simply B&W from developer Mr. B. Ware is a simple yet effect black and white app for the iPhone, and this weekend you can grab yourself a copy from the App Store for nothing, yes, that's right this app is FREE right now, so if you don't already have a copy, then what are you waiting for!!
App Store Link: Simply B&W; Sales Price: FREE
*** UPDATE ***
It looks like this app came off sale early, sorry about this.