You can also record yourself on the site using both audio and video / web cam and then upload and share your recordings with other users. Once you create an account you can also rate other people's recordings and leave comments for them. I felt that the site had some quite useful features to help students develop their English, so I have written about it on my learning technology blog and added some ideas and tips for how to use the site with students:
I'd really like to hear from anyone else who uses karaoke with their student, especially if you would like to share some ideas for how to get the most out of this.
You can see the karaoke site at: http://www.redkaraoke.com/
hope you find this useful