United3dArtists

I know someone was compiling a list of 2D programs, but I can't find it, so here is another one.
Feel free to copy/cross post/ add this to your list.

If you're a fan of movies like 'Spirited Away', then go get the (now free) software used in it.
OpenToonz

It's already in my 2D list program but need to change the link for the english page, some users report that this program have random crash or don't launch, but the developer listen the request users, need to wait to have a better version.