I made a network graph of xorxor's cryptocoin list (as of 5th January 2014).

http://biblioteka307.files.wordpress.com/2014/02/coin_ancestry_a.pdf

There are also separate graphs for the Bitcoin, Litecoin, and Peercoin families (corresponding to the three main innovations of: Proof of Work; Scrypt memory hardness; Proof of Stake).

http://biblioteka307.wordpress.com/2014/02/20/cryptocoin_ancestry/

Note that the graphs are single inheritance only. Reality is obviously more complicated. A crypto-currency may have many influences on its design. That would make the network more challenging to understand. (Reality is always more complex than theory...) So I tried to pick the single most direct influence. If there are errors (likely), please excuse me for that.

Thank you xorxor and all who have helped compile this list. For those who are new and trying to gain an understanding of crypto-currencies (such as myself), it is very useful.