How can I download Blu-Ray movies?
The same place you download DVDs from elnaz. There's nothing special about BlueRays, they're just bigger. You'll need a blueray burner to make copies of the blueray disc images though, but a blueray-rip can be played on any recent computer.
Depending on where you live, downloading movies may be illegal. Finding good, free movies that are legal to download and actually worth watching are very rare. A good free, legal movie you could download is "The Tunnel". http://www.thetunnelmovie.net/
If you want legal movies, you'll need to buy them. http://www.cinemanow.com/http://www.blockbuster.com/download