The FreeBSD Foundation has put out their year-end fundraising campaign. The FreeBSD Foundation sponsors development of the underlying OS that pfSense is based on. We made a donation as we do every year, and we encourage our users to do the same. They are a 501(c)3 non-profit organization, so US contributors may be able to deduct contributions on their taxes.
pfSense could also use your direct donations to fund general expenses, project development and needed equipment. You can donate directly to us here, though note we’re not a 501(c)3.