Ancestry.com, both its web app and iPhone app. This is a little different than most other responses in the thread, but I'm absolutely astounded how smoothly it

Ancestry.com, both its web app and iPhone app. This is a little different than most other responses in the thread, but I'm absolutely astounded how smoothly it works -- sure, you end up with some weird entries (husband/wife get tagged as the opposite in a marriage record or something), but the more I use Ancestry the more I'm convinced it's the best piece of software I've ever used. I'd break down my amazement into a few categories: --Discovery. The search function has some weird responses sometimes, but I'm astounded how frequently the "Hints" feature finds documents about relatives that I'd never have found on my own. Ancestry's search has a huge understanding of which names might be mixed up with others -- I once found a census record from the late 19th century that had both a husband AND wife's name incorrectly tagged, but Ancestry found it anyway. --Intuitive interface. After some initial confusion on the mobile app, it's been smooth sailing. Not only can you pull facts out of documents and attach them to relatives, but Ancestry preserves the "citations" so you can go back and figure out, "hm, how do I know so-and-so's birthday?" or "which facts did I already pull out of this record?" You can also link one record to multiple people in one action. --An unimaginably broad corpus of documents. This one isn't really the software, I guess, but the amount of data Ancestry has access to is unbelievable. I figured out my great-grandmother had a child as a teenager (with a man who was not my great-grandfather) that nobody in my family ever talked about. I found the full text of a 300-year-old will from my sixth great-grandfather while I was sitting on my toilet. Anyway, it's good.