As far as standalone and individual inserts go, I have to say, YouTube has been a saving grace in that department, and sawing14s has perhaps been the biggest champion this, because thanks to him, I've been able to see certain inserts again that memories of were so vague nobody else knew what I was talking about.
Case in point: I remember among my early years here at MC, I tried to jog people's memories of a particular insert I remember seeing approximately once as a tot but it was engraved in the back of my mind. In said insert, I remember Cookie Monster was sleeping over with Ernie and got afraid of seeing things in the dark and crashed through the door when running away. Unfortunately, people here weren't exactly sure what I was talking about, because apparently Cookie often spent the night with Ernie, so I could have been talking about any number of inserts (and nobody remembered the one I had described); but sure enough, ten years ago, sawing14s uploaded it, and it's still up to this day:
And just as I had remembered it from my toddler memory, Cookie Monster was afraid of what looked like a scary monster, but was actually a shaggy blanket, and he left a self-shaped whole in the door.
So yeah, despite the fact that none of us have any permission to upload anything SST related (Shane may or may not have a free pass since they actually know he's MarshalGrover and pretty much the leading SST expert on the internet), YouTube has still been a wonderful tool for us Sesame fans to relive certain moments buried deep within the bowels of our memories. To a lesser extent, the Twin Beaks Monsterpiece Theater is another such for me: like the above-mentioned insert, this one I also only remember seeing approximately once as a tot, but it stuck in my mind because of the creepy/scary-sounding music cue used in it, and Cookie actually playing a major role in it as well (I mean how often did he do that?)