A blog launched this week, thetweethereafter.com, captures some of those final 140-character comments as part of an unusual tribute to the newly departed.
"What do you have up your sleeve for your love tomorrow??? #getexcited #ValentinesDay," was the final message from Reeva Steenkamp, the model and girlfriend of South African Olympic star Oscar Pistorius, who was killed in a Valentine's Day shooting in which her boyfriend is charged.
Michael McWatters, a technology professional, said he had been collecting these tweets with colleague Jamie Forrest, "not sure whether our project was something we really wanted to announce formally or not."
But he said the "grim tragedy" in South Africa prompted them to make the site public.
"In many of the tweets there you'll likely find no deep meaning. In others, however, lie fascinating, inspiring, frightening, and perhaps tragic insights," he said.
Caleb Moore, a snowmobile racer who died of injuries sustained in a crash during the Winter X Games in Aspen, Colorado, said in his last twitter message, "Check out my fan page!" and provided a link to a Facebook site.
Aaron Swartz, the internet freedom activist who committed suicide as he faced criminal prosecution, also wrote an innocuous message in his final tweet.
"Diehl, Rittenhouse, Patterson, Ross, Sims," he wrote in response to a question, "what are your top five US Mint directors?" during a discussion on #mintthecoin, a topic related to a potential trillion-dollar coin which could be minted to avoid a US budget crisis.
Spanish mountain biker Inaki Lejarreta, 29, wrote a somewhat more ominous last tweet before being fatally injured by a car: "Windy morning. It looks dangerous to do outside training, so I start with Gym and after that, we'll see."
Forrest said of the project, "As our lives become increasingly transparent on sites like Twitter and Facebook, we leave indelible marks on the Internet that can't be erased once we die."
He said the idea was sparked a year ago when "conservative blowhard Andrew Breitbart famously sent an apologetic tweet less than an hour before he died of a heart attack."
"The site is certainly morbid, sometimes interesting, quite often meaningless. But we hope it makes you think a little bit," Forrest said.