Consider the abacus. Developed perhaps as long as 4,500 years ago, this handy gadget served the mathematical needs of merchants and accountants until the development of mechanical calculating machines in the 19th century. But the abacus hasn't been forgotten. Instead it still lives on in niches -- for instance teaching preschoolers the basics of counting.
There are a number of obsolete technologies and gadgets that have persisted from slightly less ancient times right down to the current day, though again in greatly diminished numbers and scope. A brief tour through these technological fossils serves as a lesson on the durability of items we sometimes think of as ephemeral.
Plugboards still plugging along
The world of retro computer geeks was thrown into a tizzy a couple of years ago with the report of an IBM 402, a model first introduced in 1948, still in use in the wild. Sparkler Filters, a Texas company that has manufactured water filtration equipment since 1928, still uses one of these punchcard machines for its accounting, and not even a delegation from a hobbyist group could convince them to give it to a museum and replace it with a modern computer.
In a strict sense, an IBM 402 isn't even a computer -- it's a tabulating machine, "programmed" by arranging wires on a plugboard. Some of the operations it can perform have analogies in modern database operations (the Wikipedia article on the subject is a good introduction). They were quite reliable, and if you only need one to do one task, and it still works, then why replace it? That seems to be the attitude at Sparkler Filters, at any rate.
Sparkler Filters seems to extend this philosophy to other aspects of its tech as well; for instance, its Web page appears to have not been redesigned since 1998.