Which Software Patents Are Worthwhile?

Dan Jagnow asks: "The USPTO issuing brain-dead patents is a recurring theme on Slashdot, as is the question of whether software patents ought to be issued at all. To turn the question around, what are some software innovations (historical or potential) that Slashdot readers feel merit patents?" I feel it quite reasonable to ask this question. If we must have software patents, and currently the USPTO feels this is so, then I would like to know which software patents you all feel are worthy of the name.