http://www.learnenglish.de/pronunciation/phoneticpage.htm
Why is pronunciation so important? Listen to these discussions:
http://www.bbc.co.uk/worldservice/learningenglish/grammar/pron/progs/prog1.shtml
How many different accents do you know? Here's a site where you can listen to all sorts of accents:
http://www.world-english.org/listening.htm