The Vilamovian language seems to be interesting - it is spoken only by a minority of Dutch origin, only in one town and almost only by old people. However, I know there are some Unilang members who wish to get to know it. Unfortunately - there are almost no materials. I'm posting here everything useful for you that I found.
* Vilamovian-Polish-German-English dictionary
* A collection of poems in Vilamovian, translated into Polish and German
* Some recordings of poems given above (you just have to click "Pobierz")
I'm not a native speaker of Vilamovian - I just have a very basic level of it.