Various Katas
http://osherove.com/tdd-kata-1/
https://github.com/7digital/kata-checkout
From Uncle Bob: http://butunclebob.com/ArticleS.UncleBob.TheBowlingGameKata
PDF versioned in bowling_game folder
The well known FizzBuzz Kata (http://codingdojo.org/cgi-bin/index.pl?KataFizzBuzz ) with the BANG (if multiple of 7).
Using responsability chain to handle the 'combinatorial explosion' of adding rules linearly.
Fizzbuzz Kata developed strictly following the Open/Close principle.
From Uncle Bob: http://butunclebob.com/ArticleS.UncleBob.ThePrimeFactorsKata