I was looking at the IndieCade resource page (https://www.indiecade.com/climate-jam/resources/) and noticed a few key resources that were missing.

2D Tools:
Inkscape - vector art software (free open source alternative to illustrator) https://inkscape.org
GIMP - photo manipulation (free open source alternative to photoshop) https://www.gimp.org
Paint.Net - Like MS Paint, but all grown-up (free) https://www.getpaint.net

Audio Tools:
BeepBox - Digital Audio Workstation/DAW (free open source online) https://www.beepbox.co
LMMS - Digital Audio Workstation/DAW (free open source) https://lmms.io
CakeWalk - Digital Audio Workstation/DAW (free professional) https://www.bandlab.com/products/cakewalk