would anyone happen to know of any good online resources for learning languages such as Valencian, Catalan, Asturian and Aragonese. That are preferably free.

For Catalan, there's parla.cat. (You really don't need a separate course for Valencian since it differs only in some details of pronunciation, the forms of a few words, and a few instance of word choice. Estuary English and General American diverge more than do Standard Catalan and Standard Valencian.)