There are a number of Unitarian / Unitarian Universalist congregations and associations throughout the world. Each has their own national or regional organisation.
The most sensible place to find details is through the website of the:
International Council of Unitarians and Universalists (ICUU)
The ICUU was founded in 1995 to foster the growth of the Unitarian and Universalist cause worldwide through a range of activities, encouraging grass-roots participation.