Hey,

Since I'm on the Playstation kick, I'm trying to throw together a list of demo discs for the system. I'm only counting standalone demos (so nothing already on my main psx list like the Dino Crisis demo packed in with RE3), and not counting prototypes, review copies, kiosk discs or anything like that. Also, NSTC-U games only.

Here's what I've managed so far:

"Ape Escape: Demo CD"
"Burning Road"
"Colony Wars: Vengeance"
"Contender"
"Developer's Demo Disc" (Also called the "Black Ice" CD or the "Hear it Now, Play it Later" CD. Includes the famous T-Rex demo.)
"Final Fantasy VII: Squaresoft of Playstation Previews"
"Gran Turismo: Demo Disc"
"Grind Session"
"Hot Shots Golf 2: Demo CD"
"Interactive CD Sampler Pack Vol. 1"
"Interactive CD Sampler Pack Vol. 2"
"Interactive CD Sampler Vol. 10"
"Interactive CD Sampler Vol. 3.0"
"Interactive CD Sampler Vol. 3.5"
"Interactive CD Sampler Vol. 5"
"Interactive CD Sampler Vol. 6"
"Interactive CD Sampler Vol. 7"
"Interactive CD Sampler Vol. 8"
"Iron & Blood"
"Jet Moto 3: Demo Disc"
"Legend of Kain: Soul Reaver: Demo CD"
"Legend of Legaia"
"Lunar: Silver Star Story Complete: Demo CD"
"Medievil: Demo CD"
"Megaman Legends 2"
"Megaman Legends 2 Demo"
"MLB 2001: Demo Disc"
"Namco Cool Games Free Stuff Demo CD"
"NFL Xtreme 2: Demo Disc"
"NHL Faceoff 2000: Demo Disc"
"Nightmare Creatures: Demo CD"
"Nuclear Strike: Collector's Demo"
"Official U.S. Playstation Magazine Demo Disc 1"
"Official U.S. Playstation Magazine Demo Disc 10"
"Official U.S. Playstation Magazine Demo Disc 11"
"Official U.S. Playstation Magazine Demo Disc 12"
"Official U.S. Playstation Magazine Demo Disc 13"
"Official U.S. Playstation Magazine Demo Disc 14"
"Official U.S. Playstation Magazine Demo Disc 15"
"Official U.S. Playstation Magazine Demo Disc 16"
"Official U.S. Playstation Magazine Demo Disc 17"
"Official U.S. Playstation Magazine Demo Disc 18"
"Official U.S. Playstation Magazine Demo Disc 19"
"Official U.S. Playstation Magazine Demo Disc 2"
"Official U.S. Playstation Magazine Demo Disc 20"
"Official U.S. Playstation Magazine Demo Disc 21"
"Official U.S. Playstation Magazine Demo Disc 22"
"Official U.S. Playstation Magazine Demo Disc 23"
"Official U.S. Playstation Magazine Demo Disc 24"
"Official U.S. Playstation Magazine Demo Disc 25"
"Official U.S. Playstation Magazine Demo Disc 26"
"Official U.S. Playstation Magazine Demo Disc 27"
"Official U.S. Playstation Magazine Demo Disc 28"
"Official U.S. Playstation Magazine Demo Disc 29"
"Official U.S. Playstation Magazine Demo Disc 3"
"Official U.S. Playstation Magazine Demo Disc 30"
"Official U.S. Playstation Magazine Demo Disc 31"
"Official U.S. Playstation Magazine Demo Disc 32"
"Official U.S. Playstation Magazine Demo Disc 33"
"Official U.S. Playstation Magazine Demo Disc 34"
"Official U.S. Playstation Magazine Demo Disc 35"
"Official U.S. Playstation Magazine Demo Disc 36"
"Official U.S. Playstation Magazine Demo Disc 37"
"Official U.S. Playstation Magazine Demo Disc 38"
"Official U.S. Playstation Magazine Demo Disc 39"
"Official U.S. Playstation Magazine Demo Disc 4"
"Official U.S. Playstation Magazine Demo Disc 40"
"Official U.S. Playstation Magazine Demo Disc 41"
"Official U.S. Playstation Magazine Demo Disc 42"
"Official U.S. Playstation Magazine Demo Disc 43"
"Official U.S. Playstation Magazine Demo Disc 44"
"Official U.S. Playstation Magazine Demo Disc 45"
"Official U.S. Playstation Magazine Demo Disc 46"
"Official U.S. Playstation Magazine Demo Disc 47"
"Official U.S. Playstation Magazine Demo Disc 48"
"Official U.S. Playstation Magazine Demo Disc 5"
"Official U.S. Playstation Magazine Demo Disc 50"
"Official U.S. Playstation Magazine Demo Disc 52"
"Official U.S. Playstation Magazine Demo Disc 54"
"Official U.S. Playstation Magazine Demo Disc 6"
"Official U.S. Playstation Magazine Demo Disc 7"
"Official U.S. Playstation Magazine Demo Disc 8"
"Official U.S. Playstation Magazine Demo Disc 9"
"Pac-Man World: Demo CD"
"Pizza Hut: Disc One"
"Pizza Hut: Disc Three"
"Pizza Hut: Disc Two"
"Playstation Picks: Blue"
"Playstation Picks: Green"
"Playstation Underground Jampack Fall 2001"
"Playstation Underground Jampack Summer 2K"
"Playstation Underground Jampack Summer '99"
"Playstation Underground Jampack Vol. 1"
"Playstation Underground Jampack Vol. 2"
"Playstation Underground Jampack Winter 2000"
"Playstation Underground Jampack Winter '98"
"Playstation Underground Jampack Winter '99"
"Playstation Underground Vol. 1"
"Playstation Underground Vol. 1.2"
"Playstation Underground Vol. 1.3"
"Playstation Underground Vol. 1.4"
"Playstation Underground Vol. 2.1"
"Playstation Underground Vol. 2.2"
"Playstation Underground Vol. 2.3"
"Playstation Underground Vol. 2.4"
"Playstation Underground Vol. 3.1"
"Playstation Underground Vol. 3.2"
"Playstation Underground Vol. 3.3"
"Playstation Underground Vol. 3.4"
"Playstation Underground Vol. 4.1"
"Playstation Underground Vol. 4.2"
"Playstation Underground Vol. 4.3"
"Playstation Underground Vol. 4.4"
"PSOne Demo Disc"
"Rascal Demo CD"
"Rayman"
"Speed Punks: Demo CD"
"Spyro the Dragon"
"Syphon Filter: Demo Disc"
"Thousand Arms Demo CD"
"Titan A.E. Demo CD" (Titan A.E. was never released in final game form.)
"Tomba!"
"Toys 'R' Us: Attack of the Killer Demos"
"UmJammer Lammy: Demo CD"
"Wild Arms 2: Demo Disc"

I know all of these were released, though if the title is slightly off, let me know. Any other demos you own that were standalone releases, post here and I'll throw them on the list. I know there's many missing (for instance, I'm pretty sure there's an Interactive Sampler 4 and 9, but haven't seen them).