Delimited continuations have been implemented in the de-facto standard Haskell runtime system, the GHC runtime system [0]. The goal was to make effect systems more performant [1], but I believe that work has stalled due to the maintainer shifting priorities.
Well the delimited continuation primops are there in ghc for anyone to use. But even with the proliferation of effects libraries in Haskell, I haven't heard a whisper of any of them using the delimited continuation primitives in ghc. There was one very expwrimental extension to Bluefin from memory, but that's it.
That's Bluefin Algae, which isn't as such an extension to Bluefin, but a library that wraps delimited continuations in a Bluefin-style API. As far as I know, no one has really used it yet.