general
- Fandom (wikis and walkthroughs)
- The Library of Congress (massive archive of many types of media)
- MasterWiki (MasterClass content presented in a WikiHow format)
- My Retro TVs (retro television emulator)
- Priyom (numbers stations info)
- solitr.com (browser-based solitaire, spider, mahjong, and sudoku)
- SuperCook (recipes in reverse)
- The Video Game Museum (video game info and screenshots)
- word.golf (browser-based word relation game)
outdoors & travel
- Atlas Obscura (unique places and foods from around the world)
- Bass Resource (bass fishing info)
- Roadside America (cool places in North America)
- Take Me Fishing (fishing licenses and more)
- Wikivoyage (worldwide travel guide)
religious
- Catholic Answers (Catholic apologetics)
- USCCB (United States Conference of Catholic Bishops)
visual art
- AutoDraw (converts rough sketches to clean .pngs)
- CARI Index of Aesthetics (the title says it best)
- Enchanted Learning (visual dictionary and more)
- GifCities (thousands of .gifs from the Internet Archive)
- GUIdebook (archive of graphical user interfaces)
music
- AutoChords ( )
- Citizen DJ (browser-based beat machine with public-domain samples)
- Music Theory (music theory info)
- Musicmap (visual guide through music genres)
- Online Sequencer (browser-based music sequencer)
- Radio Garden (worldwide radio)
- Radiooooo (international hits from any decade)
tech
- Information Mesh (timeline of web history)
- The Malware Museum (harmlessly emulates viruses in-browser)
- NeoCities (where we are now)
- Vimm's Lair (video game console emulators and ROMs)
- The World Wide Web Project (the first website)
each website listed here provides much, if not all, of its content for free