The Voice of America website has some excellent stories that you can use to listen to American English.
I especially like the series titled Words and Their Stories. This series has stories with idioms, phrasal verbs and stories that describe American culture.
Keep this in mind though: the narrators who read the audio tend to speak a bit slowly. You won’t always hear the linking and reduced sounds that you would in conversational American English.
To read related information on American English pronunciation click on the links below. The 0 means closed for comments.