According to irs.gov, there are volunteers at certain organizations that will give free tax preparation to those with income less than $39,000, the elderly, and military personnel and their families. The three organizations offering this service are:

Volunteer Income Tax Assistance Program (VITA)

Tax Counseling for the Elderly (TCE)

Armed Forces Tax Council (AFTC)

More info can be found at: Free Tax Return Preparation For You by Volunteers