Coding

W3Schools: great if you need a code reference and/or are learning how to code
123guestbook: free and easy guestbook service
Web Accessibility Evaluation Tool: exactly what it says, it points out potential accessibility issues on your site
Web Neko: cat that will rapidly approach your site viewers cursor
Girb: girb.

Site Graphics

Glitter Graphics: A big archive community for graphics
Background Archive: for all your background needs
The 88x31 GIF Collection: Has all the 88x31 GIFs you need!
Moremoji: some emojis
Mutant Tech: more emojis
Web Neko: cat that will rapidly approach your site viewers cursor

Mental Health + Distractions

You Feel Like Shit: an interactive self-care flow chart, helps me a lot
jspaint: windows98 paint in your browser!
feeels: self-care tool to check in with yourself on an emotion wheel