Wôpanâak

Grammar

A grammar of the language published in 2000 as an MIT thesis is available online here. Most other resources I have found at this point are the sources used to develop this grammar.

Additionally, Volume 2 of Native Writings in Massachusett contains a "Grammatical Sketch" based on several centuries-older grammars.

Dictionary

The Natick Dictionary, published in 1903, appears to be a dictionary of at least one form of the language available online here.

Corpora

The 1988 book Native Writings In Massachusett, by Ives Goddard and Kathleen Bragdon, is the primary source of text for the language, containing many (possibly all) surviving texts written by native speakers of the language from the 1660s to the 1750s. The book contains many documents with transcriptions, annotations, and translations. The documents are in large part legal documents, including land transactions and wills, although documents with other purposes are in the collection as well. The book was published by the American Philosophical Society and is copyrighted.