I just realized I have nostalgia for the 00s, so imma post things I liked back then. Feel free to do the same.
Legendary Frog
Back when Newgrounds was a site people went to, Legendary Frog had a sizable fanbase. Although in retrospect his early animations were technically crude, his humor stands up. I checked his website and it's good to see he's still making videos.
Homestar Runner
It's long gone now, but I still have a soft spot for Homestar Runner, especially the Strong Bad emails. The animation holds up surprisingly well and the humor is as good as ever. Back in the day, I even bought Poker Night at the Inventory and the first episode of the Strong Bad game.
Animutations
There once was a website called Albino Blacksheep. They hosted Flash animations of varying quality. For a couple years, there was a fad of making these bizarre, fast-paced videos. I watched the same dozen or so over and over again.