Floppy discs were great fun, I loved them. Dial-up internet can rot in its cold grave, hated that trout. Blockbusters was good, it's easier to get a sense of what you're looking for when movies are laid out physically in front of you then if you're just scrolling through Netflix. Getting photos developed was brilliant, you had no idea whether the photos you were going to get were great or absolute garbage. And when you picked them up from Boots, they came in a neat little folder. Don't really remember fax machines, to be honest, I was too young to be in a position to have to use those, really. Only ever saw a rotary phone as a retro statement: they weren't really a thing by the mid-90s, the vast majority of people had push-button.

Me taking this possibly a bit too seriously: some technology that might become obselete within the next 50 years

Scientists have invented a sieve with holes so fine that they can filter the salt from sea water, turning it into fresh, potentially drinkable water. So, hopefully prohibitely expensive desalintation will become obselete, and people dying of dehydration will be a thing of the past in the not-so-distant future.
http://www.bbc.co.uk/news/science-environment-39482342

Physical memory storage could well become obselete, at least for the general population. More and more data is being stored on "the cloud". Obviously, this does mean that the data is being stored in a physical device somewhere, but I expect that consumer technology will rely more and more on cloud storage and increasingly less on having inbuilt memory storage.

Perhaps even external computers full stop could become obselete. By which I mean, people might have computer chips in their brains, which they interact with through augmented reality displays.

Possibly nuclear fission reactors. Cold fusion - i.e nuclear fusion which uses less, ideally significantly less, power to initiate than it produces - could be just around the corner, relatively speaking, although it's seemed like it could be "just around the corner" on and off for decades, so who knows.