I've donated money to a couple of institutions (one for poor kids, other for reforestation), but I only do it in the scarce times I'm secure of my income. Which I'm totally not right now.

Also, if a beggar gets to convince me (because there are lots of scams in the train), I help them too.
If I'm on a downtown walk by myself I'll probably pay a meal for someone. ._.

Hey, I was saved some times by strangers giving me car rides!
Though all those times were in the campus, so it was less risky for both ends.