Fun fact, you can still buy new 6502 hardware from William Mensch's company. The elegance and simplicity of the core makes it virtually embedded computing "dust" in almost everything we use.
A bunch of people are still building new systems with modern twists, fixing old ones and writing software. forum.6502.org has been an invaluable resource for me building my own machine
Going up one level on that site:
http://wilsonminesco.com/6502primer/
I've been fiddling with a 65C02 over the past month. This is exactly the kind of information resource I've been looking for!
It's certainly rewarding and interesting to design the hardware and then write the software in Assembly, and helps understand how simple operating systems work.