Agh, I remember there was this little thing that let you interactively play with neuron width and add and remove nodes, but I can't find it.

Here's what else is in my bookmarks, aka what I've seen go past on here over the past few months that seemed approachably interesting:

http://www.wildml.com/2015/09/implementing-a-neural-network-... - a getting-started guide you can follow along with in IPython

https://codewords.recurse.com/issues/five/why-do-neural-netw... - just playing around, but notable

https://github.com/mbartoli/neural-animation - shows how to restyle video in manner loosely resemblant of Deep Dream

http://neuralnetworksanddeeplearning.com/ - this book is online-only but it's CC so you could legally crawl it if you wanted a local copy, I haven't rated it for my own use yet

http://nxxcxx.github.io/Neural-Network/ - a static 3D visualization you can zoom around, mostly kitsch but still kinda fun.

I recommend you go through the cream of the crop and find what suits you the most though:

https://hn.algolia.com/?query=neural&sort=byPopularity&prefi...