NASA just keeps giving and giving and giving... | MetaFilter
Free Windows-only software to browse the world via images. We don't have rocket packs, but otherwise this is starting to feel like science fiction.
Google's Keyhole may do more but it's not free and used to be picky about hardware. (Also Windows only.)
Too much map and imaging stuff is Windows only. One of my favorite pieces of software, Microsoft Trips and Streets, is (surprise) also Windows only.