Sorry if this was already posted, but I didn't see it:

There Will Come Soft Rains by Sara Teasdale

There will come soft rains and the smell of the ground, And swallows circling with their shimmering sound;

And frogs in the pools singing at night, And wild plum trees in tremulous white,

Robins will wear their feathery fire Whistling their whims on a low fence-wire;

And not one will know of the war, not one Will care at last when it is done.

Not one would mind, neither bird nor tree If mankind perished utterly;

And Spring herself, when she woke at dawn, Would scarcely know that we were gone.

There's also a short story by Ray Bradbury with the same title that quotes the poem.