Neural network freeware for building prediction and classification models in Excel. Uses backpropagation. Can handle missing values and categorical data. http://www.geocities.com/adotsaha/NNinExcel.html
Open-source neural network library for C++ (Windows and Linux). Support for MLP, RBF and Hopfield networks. Interfaces with Matlab's Neural Network Toolbox. http://annie.sourceforge.net