Le Net
Yann LeCun and others developed a really good
recognizer for handwritten digits by using
backpropagation in a feedforward net with:
Many hidden layers
Many pools of replicated units in each layer.
Averaging of the outputs of nearby replicated
units.
A wide net that can cope with several
characters at once even if they overlap.
Look at all of the demos of LENET at
http://yann.lecun.com