Passport and identification policies have changed, especially for land travel between the U.S. and Canada. Check out http://travel.state.gov for the latest rules regarding passports and identification requirements while traveling.
New TSA rules require that the name on your passport/legal ID matches the name on your ticket (including middle names). New rules also require that your gender and birth date be submitted to the airline at the time of ticketing. Coming soon…airlines will begin asking for passport numbers for international travel.
Most countries now require that your US passport be valid for six months after you return to the US.