Ephemera
I've been thinking about the details of my life that are disappearing. Examples:

Cassette tapes
When I was a teenager, I bought all of my music on cassette tapes. I still own a few hundred cassettes--many of them with music I don't have in any other format. But I haven't listened to cassettes in years. I'm not sure how readily my children will learn about cassettes--I can think of more films that show vinyl records than I can think of films that show cassettes.
(An NPR story last night pointed out that along with the decline of cassettes came the decline of boom boxes.)

Phone Dials
Even when I was a kid, telephones with a rotary dial were on their way out. But my family had a rotary phone until about the time I went to college.
Rotary-dial phones are just about extinct, but the terminology lingers on. I wonder if folks in rural third-world populations who have never had a phone before the introduction of cellular phones still speak of entering phone numbers with a term that originated with manipulating a round dial.

Line Noise
I got accosted by someone named Deathpickle in WoW, who whispered me a string of random non-English characters. I described it as "line noise", and then found myself wondering what fraction of WoW players would recognize what I meant by that.
What I mean, specifically, is the pattern of gobbledygook characters that would interrupt text transmitted over a modem when the signal wasn't clear. For example, if you were dialed into a terminal server and someone lifted the phone handset, your text would be interrupted with a slew of gibberish.
It wasn't random, as I remember it; ~'s seemed to predominate, and {'s were common as well. It was certainly a qualitatively different sort of gibberish from the 'akdflajkjl fakjld' that you'd get from a human wiggling their fingers at a keyboard.
But my memory is inadequate to characterize it exactly; I haven't seen line noise in almost a decade. And I doubt much has been preserved for posterity. This may be as foreign to my children as the chagrin of dropping a stack of Hollerith cards is to me.
(On a similar note, digital television signals will put a final end to snow on television sets. Digital transmission shows transmission failures in different ways.)

Incandescent Light Bulbs
Most of the light bulbs I've encountered in my life have been incandescent bulbs. But incandescent bulbs are being phased out. By 2014, I'll buy compact fluorescents for almost every case where I currently buy incandescent bulbs.
There'll be a few details of the experience of incancescents that will go away, though. Incandescent bulbs darken as they burn out, and burned-out bulbs have a distinctive tinkle when you shake them--neither of these are true of compact fluorescents. Those details of light bulbs will be foreign to my children.

The thought crosses my mind that these last two examples are particularly examples of failure modes going away (being replaced by new failure modes). I could probably follow that to several other examples, like the horizontal line that a cathode-ray television or monitor would display as it warmed up, or the chatter of a floppy disk drive reading data. (For that matter, floppy disks could get an entry all their own. It may be a decade since I've put a floppy disk in a drive.)