You cannot deduct the value of your time or services, including:
Blood donations to the Red Cross or to blood banks, and
The value of income lost while you work as an unpaid volunteer for a qualified organization.

A number of expenses are deductible like some of the expenses paid for students living with you, out-of-pocket expenses in giving services, including some travel expenses are tax deductible when they involve a qualifying organization. Visit their website for complete rules and regulations.

This information is from IRS Publication 526.