Volunteer expenses for charity

[kathyruvolo]

I travel from the US to Africa once a year.   The purpose of this trip is volunteering for a non-profit organization.  The entire trip is spent volunteering (not vacationing).  What expenses can be deducted, and is there a per-diem for meals or do you need actual receipts?   Finally, Where on Schedule A do you report these expenses (airfare, meals, etc.)

[kathyruvolo]

to add to my question above, the non-profit is a 501c3 organization.