Giving to a good cause makes everyone feel good but with money tight, it might be difficult to fit extras in your budget right now.
Donating blood is actually good for your health and doesn't cost anything other than a little of your time.
I have donated and from personal experience know it is painless and quick.
Some of the blood banks are non-profits so check them out before you go. I prefer a non-profit. You can donate every 56 days.
To find a blood bank near you, go to americasblood.org.