The fastest and most comprehensive i know is this chinese one. It's better than those above mentioned (I have no reason to promote it other than i like my scores fast) they do occasionally make an error but it's normally corrected pretty quickly. All live scores have that problem.
Has been mentioned but I use flashscore.com. It's useful for soccer and tennis scores... and you can pick which teams you want to be alerted to when there is a goal in their game.