Cheerios
I remember a whole series of chalkboard stick figure yodeling ads from when I was a kid (in the early 80s), but not any specific entries from the series. So... here's a random one. Then a 2014 ad featuring Grumpy Cat. (I'm sure I've seen other good Cheerios ads over the years, but none come to mind, right now.)

Cracklin' Oat Bran
Couldn't find my favorite one on YouTube, so here's a link to Retro Junk.

Crispy Critters

Eggo
Here's a playlist of Eggo ads. At least one is from the late 80s, several from the 90s, at least one from the early 00s, and one from 2014. I'm sure there have been plenty of other Eggo ads I've seen, both nostalgic and modern. They all tend to be cheesy but amusing. Maybe I'll add some more to the playlist sometime.

Froot Loops
A fun ad from 2014. Mmmm... tastes like nostalgia.

Frosted Flakes

Jimmy Dean
There's a whole series of ads with this guy in a sun costume, and the ads are all fairly cute, but I don't tend to find most of them really memorable. I do quite like the one where he has a staring contest with his wife, though. Unfortunately, whenever I find it on YouTube, it soon gets deleted for copyright violation, and for a long time it wasn't on Jimmy Dean's official YouTube page, either. But it's there now. Hopefully it stays there.

Lender's Bagels
Murray Lender did any number of commercials over the years, most of which I probably never saw. But the one that I definitely remember is this one:

Life

Nut & Honey Crunch

Nutri-Grain
A cereal bars ad from 1991, which has Betsy Randle in it. (I remember liking her in this, and maybe a couple years later she got a regular role on Boy Meets World.) Then an ad from 2013 for Nutri-Grain fruit crunch bars, about a family of vampires (the Mortons). I had a playlist of Mortons ads, but it stopped working. Then I could just find one of them on YouTube, and another (longer) one on Vimeo.

Quaker Oats
I mostly associate Quaker ads with Wilford Brimley, but I don't have any of those ads here. This is a much more modern one: Quaker Up - "The Hill." Because imagination is awesome. (see also snacks)

Raisin Bran
I just think the father/daughter relationship in this ad is pretty cute.

Rice Krispies

Super Golden Crisp
Whenever I hear the Elton John song "Someone Saved My Life Tonight," I think of this cereal.