Make a contribution. Another way you can take a stand at an individual level is by contributing money to a group or campaign that is trying to correct an injustice. If you can afford it, consider a financial contribution to a group you think is doing good work.
Do some research and find a group you like. There are groups out there working on almost anything you can think of, whether its bullying in schools, gender discrimination, homelessness, or issues related to international politics.