There are items in Diablo 3 other than a shield that give +% block chance such as Helm of Command. Does the bonus apply when you don't have a shield equipped?
Yes. I just tried it. With shield 28%, without shield and with Helm of Command 8%. Also tried to block without a shield but with Helm of Command. I blocked attacks.
EDIT: BUT you have no block amount, so if you block, you block nothing.