Thanks to Father Deacon Lance for that Kilt website.
In general: there are a few very small pockets of Celts here and there - probably remnants of early migrations.
To this one must add the diaspora, which is probably where one would find the majority of Celts today.
Every four years there is a "Celtic Congress", hosted by a university in one or another of the Celtic countries. Don't know off-hand when and where the next one is, but I'll attempt to ascertain this information and report back. A report on the Rusyn Celts would certainly be of interest.
An tAth. Brian