When I worked at Google I would literally check the internal meme site to see if there was an outage. It was at least as reliable as the official channels.
Off the top of my head, I remember a lot based on Scumbag Steve, the Socially Awkward Penguin, Skeptical African Kid, Woody Harrelson wiping away tears with money, "So I've got that going for me, which is nice" from Caddyshack, "I'm the captain now", "That's a bold move, Cotton", and whatever this is. Mostly it was the same stuff the rest of the internet uses with a few that were pretty obscure outside Google. Oh and way more animated gifs than you see elsewhere.