Saturday mornings are for cartoons, and maybe a few live-action shows. But most importantly, they are for kids' shows. It has been this way ever and always... until it wasn't. But seriously, watching cartoons on Saturday mornings is one of the most nostalgic memories I have. Anyway... I have a page for cartoon nostalgia, but not everything listed on that page was something I saw on Saturday mornings, and there are some (live-action) things I did see on Saturday mornings that aren't on that page. Which is why I've decided to start a page about Saturday mornings, to list all the things I did watch on that most sacred day of the week, not just when I was a kid, but well into adulthood. Now, I was born in 1975, and it's quite possible I saw some things in the 70s, but I don't really remember about that for sure. So this list will start with the fall of 1980. I'll link to reviews of some specific shows that have their own pages; for shows without individual links, see the cartoon nostalgia page. (There are a few things I don't have entries for anywhere, because I don't remember them well and they were never that important to me, but if I remember them at all, I'll try to list them here. There are probably also things I did see that I've now completely forgotten about, and won't remember even when I see them listed on Wikipedia.)
Note that I'm checking Wikipedia's Saturday morning schedule to refresh my memory. I'm afraid for pretty much my entire youth, I basically only had access to CBS, so unless otherwise indicated, any show on this page was something I saw on CBS. (I also got PBS and CBC in my youth, but they hardly count. Though I think I did watch Star Trek Saturday mornings on CBC, in the late 80s and/or early 90s.) It wasn't until 1995 that I got to see some shows on other networks with any regularity, via cable, and 1997 or 98 that I got to see some things via satellite. But at that point... I really get confused about when I first saw things, because they'd rerun for years on different channels and different days. So it's possible that some of the things I list here, I actually never saw on Saturday mornings. Anyway, there were lots of things I never had the chance to see, much of which may be nostalgic to people of my generation, but not to me. But some things that aired on other networks may have been syndicated to my CBS station (and some started on another network and later moved to CBS). So... I'm listing some things on the year they premiered, even if I didn't see them until later. But in some cases I may have no idea when I saw them. And in some cases, shows debuted well before I started watching, even if they were on CBS, because I was too young/not alive yet to see them when they started. (Also note that some of these shows may have gone by slightly different names over the course of their runs.)
See also 4KidsTV, DC Nation, Discovery Kids, Fox Kids, Kids' WB, One Saturday Morning, Qubo, TNBC, and Vortexx
1980
The Bugs Bunny Show, Drak Pack, Fat Albert and the Cosby Kids, Popeye, The Tarzan/Lone Ranger Adventure Hour (Zorro added 1981), Tom & Jerry
1981
Blackstar, The Kwicky Koala Show, The Smurfs (NBC)
1982
Gilligan's Planet, Meatballs & Spaghetti, Pandamonium, Shirt Tales (NBC)
1983
Alvin & the Chipmunks (NBC; I probably didn't see it til around 1988), Benji, Zax & the Alien Prince, The Biskitts, The Charlie Brown & Snoopy Show, Dungeons & Dragons, Saturday Supercade
1984
The Get Along Gang, Kidd Video (NBC), Muppet Babies, Pole Position, Pryor's Place, Shirt Tales (CBS)
1985
The Berenstain Bears, CBS Storybreak, Hulk Hogan's Rock 'n Wrestling, Land of the Lost, Little Muppet Monsters, The Wuzzles
1986
Galaxy High School, Pee-wee's Playhouse, Teen Wolf, Wildfire
1987
ALF: The Animated Series (NBC), Mighty Mouse: The New Adventures, Popeye and Son
1988
Dennis the Menace, Garfield & Friends, Hey Vern, It's Ernest!, Kidd Video (CBS), Teenage Mutant Ninja Turtles (syndicated)
1989
The California Raisin Show, Rude Dog & The Dweebs, Saved by the Bell (NBC)
1990
Bill & Ted's Excellent Adventures, Teenage Mutant Ninja Turtles (CBS)
1991
Back to the Future, Mother Goose & Grimm
1992
The Amazing Live Sea Monkeys, California Dreams (NBC), Fievel's American Tails, The Little Mermaid, Raw Toonage
1993
Beakman's World, Cadillacs & Dinosaurs, Marsupilami
1994
Aladdin, Beethoven, ReBoot (ABC), Skeleton Warriors, The Tick (FOX)
1995
The Mask, Santo Bugito, Timon and Pumbaa, The Twisted Tales of Felix the Cat
It was probably in 1995 (when I went to college and got cable) that I started watching The Tick.
1996
Ace Ventura: Pet Detective, Project G.e.e.K.e.R.
1997
The New Batman/Superman Adventures (WB), Men in Black (WB), Pinky & the Brain (WB), Recess (ABC/UPN), Science Court (ABC), Superman (WB), The Weird Al Show
1998
Eerie, Indiana: The Other Dimension (FOX)
1999
Batman Beyond (WB), Detention (WB), Pokemon (WB), Sabrina: The Animated Series (ABC/UPN)
2000
Buzz Lightyear of Star Command (ABC/UPN), Flint the Time Detective (FOX), Jackie Chan Adventures (WB), Static Shock (WB)
2001
Cubix: Robots for Everyone (WB), Los Luchadores (FOX), Medabots (FOX), The Mummy (WB), The Nightmare Room (WB), X-Men: Evolution (WB), Yu-Gi-Oh! (WB), The Zeta Project (WB)
2002
Fighting Foodons (FOX), Fillmore! (ABC/UPN), Kirby: Right Back at Ya! (FOX), The Legend of Tarzan (ABC/UPN), Mon Colle Knights (FOX), Mucha Lucha! (WB), Ozzy & Drix (WB), Scout's Safari (NBC), Strange Days at Blake Holsey High (NBC), What's New, Scooby-Doo? (WB)
2003
Cubix (FOX), Lilo & Stitch (ABC), Megaman NT Warrior (WB), Shaman King (FOX), Sonic X (FOX), Tutenstein (NBC), Xiaolin Showdown (WB)
2004
The Batman (WB), One Piece (FOX)
2005
Flight 29 Down (NBC), G.I. Joe: Sigma 6 (FOX), Johnny Test (WB), Loonatics Unleased (WB), Magical DoReMi; Mew Mew Power (FOX), Viewtiful Joe (WB)
2006
Jane and the Dragon (NBC), Legion of Super Heroes (CW), Spider-Riders (CW)
2007
Eon Kid (CW), Magi-Nation (CW)
2008
The Spectacular Spider-Man (CW)