I have a fair bit of domain experience, and I'm going to disagree with the other people who have responded to you and argue that volunteering time is often more helpful than donating money. The efficacy of time vs. money is context-dependent and one is not better than the other.
1) How much money are we talking here? An extra thousand dollars would be meaningful to a small organization, but $50 is not going to make a difference. Something like Habitat for Humanity has thousands of people donating $50, but small organizations don't, and are constrained by lack of man hours as opposed to money.
2) Not every organization worth helping is a non-profit. Local community groups are often not non-profits or any sort of official organization at all. Once again, just because Habitat for Humanity is inundated with volunteers doesn't mean your local group investigating police corruption is.
3) Many organizations don't know how to use volunteers. This is partially because volunteers are notoriously unreliable, but it's also because most groups don't have outlets for self-motivated volunteers. These volunteers have to "create a position" for themselves, and if they're motivated enough to help but not motivated to define their jobs then they'll just lose interest and drop out.
4) A lot of organizations are composed entirely of volunteers. They might need money for something like webhosting, but they probably also need people to perform basic tasks like research or website administration. Unless you are giving the group enough money to hire a full-time staff member or something similar, there are severe limits on the marginal utility of a dollar.
5) To reiterate, not every non-profit/organization is Habitat for Humanity. There are a lot of smaller ones that need help an do good work.