In their own words, the Language Attrition Research Archive (LARA) is interested in language loss:
This site is a bibliographical source on natural language loss, maintained by the Kellogg College Centre for the Study of Lifelong Language Learning, Kellogg College, University of Oxford, in cooperation with the ELT Department at BYU-Hawai’i and Oxford University Language Centre. Our aim is to provide a research tool for those interested in the loss of languages, either in individuals (language attrition) or in groups (language shift/death). You can use the LARA Visitors’ Book to communicate with us or to tell us of items you would like included in the listings. It is also possible to use the site Data Management tool to provide entries for LARA.
They also maintain a contact list for participating researchers.