There are a number of resources that I am aware of regarding ACT workshops.

The number one place to look for trainings is on the contextualpsychology.org homepage . That's the home of the Association for Contextual Behavioral Science , the home of ACT. Many new events are being listed there all the time.

Workshops that I am doing in the Northwest USA area (usually Portland, OR) are listed on my my personal webpage at http://www.drluoma.com/ACT.html

Online trainings that will be offered throught Learningact.com are available in the events section. 

I have created a list of resources for therapists wanting to learn ACT. It provides a bunch of ideas on how to learn ACT, including what books to read, when and where to find workshops, how to find supervision, and various online resources.