We have a "Family Record" on our maternal side that was composed, starting in 1840, by a foresighted forebear, Rep. Samuel Jones. (One of 5 generations of Samuels in a row, so for starters, it helps ID which Sam'l was which.) It was transcribed some years ago via typewriter and we now have it in electronic form so it can be shared around the family, and it's been a tremendous help with about a dozen profiles... mostly confirming information that did exist elsewhere, but sometimes providing dates -- or confidence in dates -- that we did not have before.
I also have, courtesy of my sister, a stack of notes and letters from/to my maternal grandfather and several of his siblings that are a) fascinating [e.g., the note his youngest brother evidently left at their mother's bedside while she slept, joyfully announcing his engagement], and b) helpful in confirming dates, place names, and nicknames, and more. I need to dedicate a day to scanning all of these... and apparently there are "more where that came from"...