Web Graphics

Glitter Graphics Sizable repository of graphics, GIFs, layouts, backgounds, sparkles, and pretty much anything you need to make your website (or myspace) look pretty!
GifCities Large tag-searchable archive of all GIFs from archived GeoCities pages
SadGrl Online Extensive webmastery tools and resources. From layout builders and HTML/CSS guides to tiled backgrounds and free fonts!
Favicon Maker Simple tool for creating 16x16 favicons (even animated ones!)
Backgrounds Archive Archive of tileable and desktop backgrounds
Yesterweb Large ~600 links of retro aesthetic sites
WYSIWYG Editor Online What-You-See-Is-What-You-Get editor. Makes HTML formatting for text-content easier.

Digital Art

JS Paint Win 95 MS Pain recreated in JavaScript
KidPix KidPix in all its glory from the comfort of your own web browser
Piskel Pixel art GIF maker
EZGif Simple free GIF editor with no watermarks
PixaBay Royalty-Free Photos, Music, SFX, Videos, and more

Social

SpaceHey MySpace clone circa 2009 with nearly 700,000 members. HTML/CSS customizable profiles with no ads
MelonLand Forum Classic BB-style forum focused on internet, WWW, and all things web
NeoCities Spiritual successor to GeoCities. Free website hosting with lots of resources for making your own website (this site lives there :o)

Crouton

Crouton Crouton