A wonderful way to work on improving your accent is to listen to famous speeches. I found this great website which contains hundreds of famous speeches. You can hear the audio and sometimes see the video of the speech. The best part is that each speech has a transcript with it. That way, you can practice reading it out loud.
I recommend that you listen to the whole speech several times while reading it. That way you can learn the pronunciation of some new words. Then, I recommend that you listen again, clicking on pause after some short phrases. Try to repeat the rhythm and intonation of the speaker. Pay attention to how the speaker is linking words together.
This website includes all of Obama’s major speeches and speeches from some classic American films. It can be a fun way to practice. Enjoy!!
http://www.americanrhetoric.com/
(To learn all the rules of linking, rhythm and intonation, I recommend that you purchase “The American Accent Course:50 Rules You Must Know” available at: accurateenglish.com/dvd’s.htm)