CanTex said:The very latest guidance on this is within the current "A Guide to Naturalization" which you can find here: http://uscis.gov/graphics/services/natz/English.pdf
Take a look at publication M-479, which is contained on page 59 of the Guide.
In spite of what you may see elsewhere on the USCIS web sites about the payee, follow the M-479 instructions, i.e. your check or money order should be payable to the U.S. Department of Homeland Security.