As i can see many people started involve in this Playcanvas community so i am dropping some quick links here which come handy as Game Developer.
1] Photopea [https://www.photopea.com/]:
Information: Photopea is a web-based raster graphics editor used for image editing, making illustrations, web design or converting between different image formats. Photopea is advertising-supported software. It is compatible with multiple web browsers, including Opera, Edge, Chrome, and Firefox.
In short, Photopea is Light Version of Photostop. It comes handy when i have to modify 2d image asset or UI shared by artist. Editing, resizing, cropping, changing color and lots of thing can be done on Photopea.
2] TinyPNG [https://tinypng.com/]:
Information: Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
In Short, TinyPNG is very helpful to save disk space…
Information: Free online 3D modeling software: Design, editor, animation, rendering, & lots of free 3D models. Supports Three.JS, Blend, FBX, OBJ, V-Ray, Babylon.JS, STL.
In Short, Clara.io is helpful when i want to edit 3d model or change the pivot position of 3d model.
Information: Diagrams.net is free online diagram software for making flowcharts, process diagrams, org charts, UML, ER and network diagrams.
In Short, Diagrams.net is very helpful when you want to represent some technical stuff to non-technical person.
5] Vectr [https://vectr.com/]:
Information: Vectr is a free graphics software used to create vector graphics easily and intuitively. It’s a simple yet powerful web and desktop cross-platform tool to bring your designs into reality.
In Short, Vectr helpful to create 2d art and basic logo design using basic shapes.
Hope it may help you!