I found a couple of interesting apps the other day: the first is History Timeline - it gives a well... timeline of history, and you can fine-tune it to topics like science, wars, and so forth. for example, I selected science and it tells me the first documented use of toilet paper was in China, in 589, and an early depiction of a fishing reel was in 1195. It covers many countries the second is Lifemap, which shows the known taxonomy of living things. Looking a little like a mind map, you are able to zoom in on Eukaryota for example, and find what Kingdoms comprise this Domain. I thought they might be of value to science-fiction writers, or those writing historical pieces. Both are free.