I'm looking for a good (beginner level) reference book (or website) on different types of Neural Nets/their applications/examples. I don't have any particular application in mind, I'm just curious as to how I can make use of them. I'm specifically interested in using them with Python, but any language, or even just theory would do fine.
I am currently using this site as a primer - not python, but a good feed-forward network example and pretty straightforward to follow.
At the same time I have been reading The Essence of Neural Networks by Robert Callan (ISBN 0-13-908732-X) which has a wide range of network architectures and applications and is an easy read.
Since you mention python I should direct you to this IBM site, which I found very useful and the underlying code is in python here. Citation should go to Neil Schemenauer.
I should also mention that I took the python code and ported it to numpy because it ran very slowly. I was unsuccessful, but before I rubbish numpy I have to say that I suspect my implementation was not very good and I'm sure there is a vectorised way of doing forward passes and backpropagations, I just didn't find it.
What I have ended up doing is implementing in Java by a simple port of the python code. This only took an hour or so and it runs about 100 times faster. I think this is more proof that I don't know what I'm doing with numpy, but if you are starting from scratch I would question whether raw python is the right language for you. You may be better coding this sort of thing in C or C++ if you have to use python.
Best of luck.
See the below three links for Neural Networks using Python:
An Introduction to Neural Networks
Weave a Neural Net with Python
Ron Stephens
There is quite a extensive series of courses avaliable at Heaton Research. The course is for C# (Avaliable also for Java) however it explains the concepts at length, so I suggest you take a look at it even if you will code in python yourself.
The courses are in video format, however most important concepts are also writen down.
"Programming collective intelligence" by Toby Segaran has a chapter about NN and also some examples in Python.
For better understanding of neural networks i recommend free software:
Sharky Neural Network - Neural networks in action
There are many network structures available. You can see neural network learning progress like a movie - live view. SNN is very interesting software.
I think you have the python bit covered with the answers given above. As for the "or even just theory", Raúl Rojas has a hefty ebook you can download from his wiki page.