For those who have achieved FI and find time on their hands, I suggest two opportunities to do worthwhile voluntary work on the internet.
www.zooniverse.org has several projects, from transcribing hand written weather records from US Coast Guard ships of a century ago, to extend digital weather records back in time, to interpreting Hubble space telescope images. Computers cannot yet do visual interpretation as well as people can. The method is that two or three volunteers transcribe one handwritten page of US Coast Guard weather records, and the system takes the consensus interpretation. Same with Hubble images.
Computers can scan printed books, using optical character recognition (OCR), but usually make one or two typos a page. This website
http://www.pgdp.net/c/ wants volunteers to correct typos on OCR scanned pages. You can choose which book to check.
