The BBC has the story (photo from nl.DanielPipes.org).
US Secretary of State Condoleezza Rice said she had accepted Ms Hughes's resignation "with a great deal of sadness but also a great deal of happiness for what she has achieved".
Ms Hughes was behind the setting up of "rapid response" public relations units abroad to handle news events.
She also ensured that more Arabic speaking officials were available for interview by Arabic media outlets.
However, polls suggest that the popularity of the US overseas remains low, affected by the aftermath of the Iraq war and the unresolved Israel-Palestinian conflict in particular.
Speaking after her resignation was announced, Ms Hughes said she felt she had fulfilled her mission "by transforming public diplomacy and making it a national security priority central to everything we do in government".
Ms Hughes intends to leave the state department by the end of the year, probably in mid-December.