This quick project on i-hacked.com (via MAKE blog) converts a sound source into light, ships it across the room via a simple laser pen pointer, and converts it back into sound with little quality loss.

The most common hack for dvd players is to allow multiple regions to play (dvd's intended for other countries).  Another is to disable the macrovision.

They have quite a few players listed.  As always, try at your own risk.

This site has a lot of information if you're interested in building your own LCD projector. 

It provides some drawings and plans but more importantly it has a lot of resources on the topic.

This is a great practical joke.  Attach what looks like a persons legs to a device that sits on a toilet, then strategically place speakers that play "natural" sounding sound effects on a continuous loop.  Great fun is sure to ensue.