A widely used site that has thousands of resources to help you to get your class singing. Stream and download music and find lyrics to use in your class. Use the whiteboard option to sync the music and words.
http://ictmagic.wikispaces.com/Music%2C+Sound+%26+Podcasts
This is a wonderful site from the University of Salford in the UK. Listen to soundscapes which have been recorded all over the world. Navigate on the map to find a place of interest, listen to the recording and read the information about the location. Upload your own soundscapes using the site or download the iPhone and iPad app at https://itunes.apple.com/app/i-say/id516927213. It's a useful geography resource and should get your students thinking about the sounds around them.
http://ictmagic.wikispaces.com/Music%2C+Sound+%26+Podcasts
This has many good sounds. Do not just give to students to explore for a project though. If you listen to the sounds in the Skits and Comedy section you will understand.