Check out this excellent resource:
Randall's ESL Cyber Listening Lab
There are dozens of audio dialogues for you to listen to with questions and follow-up exercises. (American accent.)
Another is
While this is designed for advanced professional students it is one of the best uses of computer technology for vocabulary improvement.
And check out this other amazing site:
Sarah, a Kiwi working in Japan, publishes a daily internet video lesson with supporting script. It is a rich mix of learning and fun. (New Zealand accent.)