I will likely send timed messages/emails to people outside of my family who have been a big part of my life, as long as I think it'd give them any sense of closure and/or keep them from worrying about me. These will be personalized (it's not very many people), explain my situation & reasonings, method, and finish off by thanking them & saying goodbye. These are people I care about or have cared about, I want them to know just how much they meant to me and what's happened. These will not be sent to people from ages ago, just current or extremely recent people.
My family knows enough, and I don't want them knowing the rest. The stuff related to them, they have been directly informed of, and have chosen to ignore & dismiss, writing it out again would just be dismissed yet again. They can live in denial, I just want out of here.
Physically (the note they'll see), I'll leave a note asking to have no funeral (or memorial of any kind), be cremated, and have my ashes spread in the mountains by someone completely external to the family. This doesn't matter hugely to me, I'll be dead, but them using my death as a reason to garner undeserved sympathy & attention (as well as "closure") when they were a major contributing factor makes me sick. They will do as they wish though, one way or another.