For open source, GitHub has a crap load of stuff that you get for free, their features beyond code, issues & PRs is pretty cool. IIRC for when you get past free tiers, they have a program for open source where you can still be eligible for more of their otherwise paid offering
As for students, if it’s code, GitHub! Other than that, Trello maybe?
I think Microsoft still also hands out license for various tools or SaaS that one could use for that. Atlassian likely too for their jira/confluence. Or just some docs in a shared Google drive