There is a resource I keep looking for but have never found yet. This is a single source of all the communities that use the extraordinary form (for all liturgy including the Divine Office) and welcome lay people in need of a period of reflection or organize retreats.
Perhaps we can start to help in the formulation of such a list by virtue of our readership contributing the names, websites and addresses of communities of men and women, who use the usus antiquior and provide facilities for lay retreats.
Speaking for my own part, I would also be interested in a listing which also included communities that are active in the reform of the reform, or which use both forms.
In view of that, perhaps our readers would like to denote whether the community is also, "reform of the reform", "usus antiquior" or "both".
These could be added to the NLM Wiki.