We track them internally. If you want to work on one, send a note to the mailing list and I'll let you know if you can start or not. Also see our list of wanted ebooks: https://standardebooks.org/contribute/wanted-ebooks

There's no subreddit but we do release announcements on the mailing list, and we have an OPDS feed you can plug in to your reading software of choice: https://standardebooks.org/opds/