Archival

BlueMaxima's Flashpoint Flash and Shockwave archive project with a frontend for downloading and running files. (tip: when you install this you can use flashplayer_32_sa.exe to run your own swf files.)

Ruffle Flash Player emulator that can be downloaded as a browser extension, for old sites or Internet Archive.

Swfchan .swf file archive (NSFW included)

How Flash Games shaped the video game industry Timeline of Flash game popularity over time, along with some developer interviews.

Web Design Museum: Flash Websites made with Flash.

Flash Websites

Newgrounds Newgrounds somehow manages to still be relevant after all these years, but here's a page all about their old Flash hits.

Albino Blacksheep Animation and games. (Mobile friendly!)

Armor Games with it's own list of classics.

Kongregate

FreeTheFlash One of the first flash sites I ever stumbled upon amazingly still exists. (Ruffle is required)

StickPage (Ruffle is required)

Andkon Arcade (Ruffle is required)

Warbears (Ruffle is required)