To my knowledge Bush has not commited any impeachable offenses. I don't care for him or his policies, but that doesn't mean that we should go impeach him.
Here's one quote for you to chew on. There are so many impeachable offenses, using forged documents and lying to Congress to get us embroiled in a tragic war, for one.
People far more learned than me who actually know the law agree that Bush has committed impeachable offenses:
Since when do POWs get trials?