I prefer volunteering to monetary donations mainly because I like to know exactly what help I have provided, and I'm a little paranoid. I never trust the organization or use of money; I've seen too many poor choices in the past.
Without volunteering, any helpful attitudes and thoughts are limited to the chance of being in the right place at the right time. Yesterday I helped a guy push-start his truck because I happened to be in the parking lot at the right time. Then, I saw a kid playing with his parents at the grocery store and he didn't see the shopping cart rolling towards his head. It was complete luck that I was there.
I'm looking forward to Saturday, there's a park cleanup/maintenance thing and everybody who visits the park will be visiting a slightly nicer forest.
Another fun one is trail maintenance. I haven't done that in over a year, but it's plain manual labor to keep a beautiful hiking path accessible. If any of you have wilderness areas nearby and like hiking, you should try it out.. you'll love it