stonecold, as has been discussed, in about a billion years the sun, our wonderful, good-ol run-of-the-mill-star, will, after gradually getting hotter and hotter, will reach a temp that will finally do the earth in. the surface water will be gone, and the earth's surface scorched, all life destroyed.
then after about 4 billion additional years, when the sun is about 9.5 billion years old, it will go nova. you are correct in the lack of mass to be a supernova statement. the inner planets will be engulfed in our star's last grasp at life. when it shrinks down to a white dwarf from the red giant stage, the earth will be unrecognizable. burned beyond comprehension.
actually, 2012 looks pretty good.