This was posted on Hacker News earlier today, and by all accounts, is fairly comprehensive.
http://www.michaelnielsen.org/ddi/how-the-bitcoin-protocol-actually-works/
While not Peercoin-specific, I felt that there’s enough of an overlap between the two coin’s underlying technologies that it would be an interesting read for anyone who wanted to dig in deeper to understanding how cryptocurrencies work.
Enjoy!