In my view, there's a bit wrong with the world and unless you find yourself in a position of immense power, either through luck or hard work, you won't be able to fix it all. So pick something, and work at it. Personally, keeping people safe whilst they sleep and helping those in need is something I want to do; and so it's part of the reason I'm applying for a commission in the forces (cue 'dirty recruitmentvideobelievingidealist speeches'). Seeing those helicopters winch people in the floods to safety and C-130 crews ferrying supplies to guys who really need it overseas really does it for me.
But even donating a few dollars to the tin rattlers at the local shopping centre makes me feel slightly better about myself. So what if only a dollar goes to the people who need it and the rest is swallowed up by bureaucracy? That's one dollar more than they had before, and it's one dollar more than the guy who walks past and doesn't donate a cent.