24 Pull Requests is a great initiative by to encourage everybody to give back to the open source projects they have been using for free all year long. Appealing to the “Christmas Spirit”, the goal is to ensure the sustainability of those projects (and make users aware of this huge problem!) by having more people contributing back to them.
All contributions will become part of your online CV (unless you prefer to remain anonymous) and there is nothing that excites more recruiters than seeing programmers participating in this kind of community actions.
You can even organize a local hackathon event local to contribute altogether!