Visual 6502

[bigsofty]

http://www.visual6502.org/welcome.html

This is a pretty amazing piece of programming IMHO. Its a 6502 simulator but its done at the lowest level possible, that is simulating the circuits on the chip, visually!  It demystifies the inner workings of CPU for me... a little.

[Hatonastick]

That is really cool! 

[ampos]

I have a book "the rise and fall of commodore". In the chapter about how they made the 6502 is amazing; it was so... "manual"...

[Ruidesco]

I have that book as well, it was an amazing read and a great insight into what went on behind the scenes.
Bagnall edited a revised version with more interviews that covers up to right before the Amiga days (the book is about the same size as the first one while covering half of the time span). The Amiga book with extended info will be available supposedly sometime next year.