http://archive.ics.uci.edu/ml/datasets.html
http://www.vision.ee.ethz.ch/~calvin/datasets.html
http://www.vision.caltech.edu/html-files/archive.html
Street View House Numbers
http://algoval.essex.ac.uk:8080/icdar2005/index.jsp?page=ocr.html
http://www.cs.toronto.edu/~kriz/cifar.html
http://groups.csail.mit.edu/vision/TinyImages/
http://www.alphamatting.com/datasets.php