There are all kinds of add-ins for databases and spreadsheets. I first heard about this stuff at a conference where a speaker was focused on Geographical Information Systems.
I have no doubt that there is a huge application for the stock market, in fact - isn't this the foundation of the quants? (keep in mind, these quants are in part, credited for much of the volatility we saw during the last pullback).
Here's a good read if your interested in the nuts and bolts of it's methodology -
http://en.wikipedia.org/wiki/Artificial_neural_network
Here's and example of the software
http://www.neuroxl.com/