Donating/Volunteering - is that a tax deduction?

I never really thought about this, but I donate/volunteer many hours every year to playing in nursing homes (as many of you do too).  I never get anything signed that says I was there...but do any of you get documentation and claim this as a deduction on your taxes?  Forgive me if I sound like a dummy.  This is probably a question for the person who does my taxes!