The default-stuffer from the Racket web server uses this approach to store serialized continuations that are too large to put in URLs directly: it saves them in files under ~/.urls/, where the name of the file is the MD5 hash of the content.
The underlying functions are provided for use in non-default "stuffers". The web-server/stuffers/store module (source) provides an interface for key–value stores and an implementation for directory-backed storage. The hash-stuffer function (source) then implements hash-addressed storage on top of it.