Reading text messages or emails while driving is illegal, dangerous and stupid, none of which stops lots of people from doing it. Free BlackBerry app DriveSafe.ly reduces the risk by reading incoming messages out loud.
As well as reading incoming messages, you can configure the application to send an auto-reply of the "I'm driving, I'll get back to you soon" variety. Operation is hands free, so the distraction factor should be lowered (though not eliminated entirely, especially if you get a lot of email).
Lifehacker HQ's BlackBerry is between SIMs right now, and in any event I don't drive. If you give this a try on the road, let us know how it goes in the comments. DriveSafe.ly is a free download for BlackBerry.