C64.com: https://www.c64.com/

For ROMS downloads: https://www.planetemu.net/machine/commodore-64

The C64 Scene database: https://csdb.dk/

The C64 Wiki: https://www.c64-wiki.com/

Lemon 64: https://www.lemon64.com/

Commodore archive on Zimmers.net: http://www.zimmers.net/anonftp/pub/cbm/index.html

Any suggestions? Send me an email at support@arcticretro.com

Emulators:

VICE: https://vice-emu.sourceforge.io/

C64 forever: https://www.c64forever.com/