yeah I use VOA all the time. If you go to the Special English section and choosing one of the articles, it will
usually have an audio clip of a reporter reading the article for you. There are various formats. You want to download the mp3 format. When you click on it, if it doesn't give you the option to save it, right-click on the link and choose "save target as." This will let you save the file. Then you need a CD burner to burn the mp3 file to a CD as a music CD. There are various ways to do this part depending on what sort of programs you have available to you.
I get the audio file and copy the article onto a word document. Then I format the document so I can make it all fit on one or two pages. I print it and we listen to the article while reading it. Then afterwards I dictate about 5 questions for them to copy down and answer in complete sentences. Or you can provide the questions beforehand to them on a worksheet or with the article.
Doing this with NPR articles is more difficult since you need a streaming audio recorder. And you can't get transcripts of the articles without paying for them.
One site I think you will like a lot is
www.breakingnewsenglish.com they also provide audio for the articles, but I like to have one of my students read the article out loud. (I also like to have a student dictate the comprehension questions as well)
Check the library of the school you are at to see if they have any TOEFL prep materials. I am making my own TOEFL prep tests from a book I checked out in my library.
I took the TOEFL last week to see what its like so I can better prepare my students. I found that a lot of the activities I already do, like the ones mentioned above are good TOEFL prep. If I were you I would get them used to the format of the TOEFL by having them do some practice tests. In each section you can cover various test skills like process of elimination, going with your first instincts, etc. On top of that I would do like you are thinking, various listening activities. And I would give them lots of reading activities too.
I think what also helps is correcting each others work. This is because on the TOEFL is a section specifically on doing that.
What could be real interesting would be to give them a TOEFL practice exam at the beginning of the course, do all your activities and practice, and then at the end give them another TOEFL practice course.