The ICU User Guide provides information on i18n topics for which ICU has services, and includes details that go beyond the C, C++, and Java API docs (and avoids some duplication between them).
This is the new home of the User Guide (since 2020 August).
The official ICU Site is located at https://icu.unicode.org. It is the official landing page for the ICU project.
Some of the pages from the ICU Site have been migrated here. The migrated sections and pages from the ICU Site are visible in the navigation bar of this site below the “ICU Site” section heading.
Other documentation pages here are written by and for team members.