I've come up with a very simple implementation of lazy monadic queues based loosely on ideas from Leon P. Smith's control-monad-queue package. This implementation ties a similar sort of lazy knot, but avoids the complexity and strictness of continuation-passing style. I'm curious whether something similar is already available on Hackage, and, if not, whether it would be useful enough to package it. The source code can currently be found at https://gist.github.com/treeowl/5c14a43869cf14a823473ec075788a74 David Feuer