this month i donated to random national parks. we've visited a few here in hawaii:
haleakala national park on maui
hawai'i volcanoes
kaloko-honolohau historial park
pu'uhonua o honaunau historical park
pu'ukohola haiau historical site
i always try to go to the visitor center at each park almost always buy a postcard or something, and when checking out, the machine asks if i want to donate so i always do. between $5 and $20, depending on my mood, lol.
i'm VERY happy i purchased an annual national parks pass! it's SUCH a good deal if you go to places like this. national parks are like $30 a pop, and national historic parks sometimes also charge. my current pass i bought at acadia last summer :)