When I was messing around with C64 programming, I used dasm (https://dasm-assembler.github.io/) and the VICE emulator (https://vice-emu.sourceforge.io/). But I'm sure there are better tools out there. This text file is a fantastic reference on the VIC-II video chip: http://www.zimmers.net/cbmpics/cbm/c64/vic-ii.txt

These are basic, but free and will get you going quickly:

CBMPrgStudio is a solid free windows app. I like cross-platform WinVICE for it's great monitor.

Once you get to be an expert, people seem to use C++ to synthesize their own 6502 routines.

Additionally: where is a good place to start for learning about C64 (demo) programming?

I recently got a cheap as chips 1541, now I just need to get ahold of my C64-C that stuck in my mother's garage about 1500 miles away!

I know my way around Amiga demo programming, but would love to have a go at C64 too.