Digital archival & related

Magazine scans (Select magazine, 90s)
Retro videogame magazine scans
Atari magazine
textfiles.com - CD dumps, zines, lots of stuff
High quality scans of videogame art
Old book illustrations
Flashpoint - Flash games archive
The VHS Vault
Commodore 64 games
Open directories - subreddit
Marginalia - A fun engine for text-heavy, small pages

Resources for artists & creatives

BLKMARKET - Very high quality textures, some free
Pixar 130 - Textures used in old pixar movies. Seamless.
Pixar 128 - Same as above.
Nintendo 64 texture libraries
More textures
Transparent PNGifier

Web games & fun stuff

Free version of NYT's Spelling Bee
Kittens game - Incremental game a la Cookie Clicker. Pretty hard.
DAN BALL - Tons of fun little games and home to the famous Dust Game.
Fully functional in-browser ver. of LSDDE
Cicada Marionette - Homepage of the creator of Crypt Worlds and altogether very fun site to explore
I don't care for H*mestuck but I love in-depth dollmakers
50 games in 2014 - Lots of tiny but addicting games by a single dev
In-browser player for over 9000 Touhou covers/arranges
Glyph drawing club - Make stuff out of ASCII-like symbols
TANE - Hard to describe. A web toy. Flashing warning.
Enigma Device - Daily brain teaser puzzles
Pointless Sites - Not pointless. Big lists of small internet curiosities
Yume Nikki Online - Coolest. In-browser versions of a YN and other fangames that you can play with others in a multiplayer experience, or by yourself. Lots of options. Probably the easiest and most accessible way to play these games nowadays.

Programs

Alchemy - Open source drawing program with a bunch of funky tools. Seemingly abandoned.
Playscii - "Draw", animate, and program with ASCII glyphs. Lots of options.
Pencil2D - Very simple animation program
Soulseek - Limewire 2