castalbums.org is a user-generated resource, describes itself as a "discography of musical theatre recordings and resources for collectors", and is a useful reference for that particular category. it provides anchored links to specific releases organized under dedicated pages to productions (the equivalent of our release groups), and offers all of the release data you'd expect from a discography site. it often also cross-references cast production recordings with associated releases that happen to contain the same recordings (say, if two or more musicals are combined into a single release, or an artist includes songs they've recorded with a cast in a personal album they've released separately).