Ancestry.com has made their entire site FREE from November 1 - 3. I have been going crazy looking up everybody that I can think of to fill in gaps. If I knew they were going to do this, I would have prepared by making a list ahead of time. Actually, I'm getting so much COMPLETE information that I have enough work just adding source documentation to my collection.
3 days is just a teaser, but I have already found the names of a pair of great-grandparents that has had me stumped for years! Woohoo!