Looking for neuronal network libraries (providing the basic multi-layer-perceptron with back-propagation and possibly teachers) i did find only libraries which seem to come from the 1990s and don't use more modern approaches (stl etc.) or small student projects.
Did i miss libraries that you know about?
update:
Support for mnist would be nice but is not necessary.
I can also search myself - it'd be interesting to hear about libraries others found very usable.