Last Thursday (Jan 18th, 2007), this is what happened with one of our Dell laptop batteries. The battery literally exploded in our user's face while he was working on his laptop that night. He wasn't hurt though, just shaken.
Laptop battery explosions aren't a myth everyone. These things really happen & I finally had a camera handy to take pics to prove it.
If you have a Dell laptop, click here to find out if your battery needs to be replaced free-of-charge by Dell.