En passant examples
http://www.chess.com/tactics/server.html?id=131399
http://www.chess.com/tactics/server.html?id=35337&practice=1
http://www.chess.com/tactics/server.html?id=175475&practice=1
http://www.chess.com/tactics/server.html?id=70740
http://www.chess.com/tactics/server.html?id=100815
http://www.chess.com/tactics/server.html?id=48276&practice=1
http://www.chess.com/tactics/server.html?id=63335&practice=1