I'm a CS student, I have some time before I graduate and have kind of dipped my toes in various things without specializing in anything. I would like to know what would be useful for the movement, so that I can use my skills to contribute.
And before people say "everything is useful"...well yeah but it's nice and fulfilling to have specific ideas I can work on learning/building myself.
Also where can I find leftist open source projects? I know lemmy and this website for one are open source but not sure of others.
No tech project is going to build socialism. Many Occupy Wall street era people tried it and it went no where. That said, in the course of building a socialist movement IRL, you'll find having tech skills are occaisonally useful, either to have an online presence like a website or to automate tedious computer work.
I cannot emphasize this enough, the less code the better. Keep project small and tight. Try to leverage existing functionality as much as possible.