If you have access to some international cable TV stations that is a great start to start listening to various accents and increase your vocabulary. While watching, you can soak up a lot of American (or British) culture.
If you don’t have access to international television, then you can go out on the web and find some great stuff to watch as well. Youtube.com is a wonderful site you can go to to view old or new videos. Just type in what you want to watch and search for it. You can search for old American shows like Dallas or 90210 or you can search for more recent shows like Desperate Housewives or Ugly Betty.