They headed a roll that included eight CBEs, 21 OBEs and 29 MBEs for services to the charity sector.
Among the CBEs were Ian Russell, chair of the Russell Commission on Volunteering, and Kevin Cahill, chief executive of Comic Relief.
Another CBE was Nina Barough, founder and chief executive of breast cancer charity Walk the Walk Worldwide. Actress Penelope Keith OBE also gained a CBE for service with a variety of national and regional charities.
Marsh was honoured "for services to families and children", and Williams "for services to people with learning difficulties".
Marsh became director and chief executive of the NSPCC in September 2000, before which she was head teacher at Queens' School in Hertfordshire and Holland Park School in west London.
"This is a tremendous personal honour, but most of all it is a recognition of the truly inspiring commitment of NSPCC staff, volunteers and supporters over many years," she said.
Williams began her career as a social worker in Shropshire, and has been the director of social services at Wigan Metropolitan Borough Council and Cheshire County Council. She became chief executive of Mencap in 2003.
OBEs went to, among others, Joyce Moseley, chief executive of youth charity Rainer, and Robert Thompson, director of fundraising at the Royal British Legion.
Margaret Cooper, chair, Independent Living Funds;
George Edington, chair, NCH;
Michael Gooley, chair, Trailfinders travel agency (for services to charity); Primrose Wilson OBE, former trustee, National Heritage Memorial Fund; Simon Maxwell, director, Overseas Development Institute; Sarah Spencer, chair, Equality and Diversity Forum.
Edna Telfer, director, Bristol Drugs Project; Moira Swinbank, chief executive, TimeBank; Kate Nash, former chief executive, Radar; Jennifer Byers, former donor services director, CAF; Patricia Heywood, former president, Mothers' Union.
Elizabeth Haddow, co-founder, and Malcolm Haddow, director, National Holiday Fund; June Sarpong, TV presenter.
(For space reasons, the list of OBEs and MBEs is not comprehensive).