Dear all, I have just released a package called blaze-builder on Hackage. It is basically a builder monoid supporting fast string concatenation. It was originally written for the blaze-html package, but because we thought it could be useful elsewhere as well, we are releasing it as a separate package. Here is a blogpost with more information: http://jaspervdj.be/posts/2010-08-05-blaze-builder.html And here is the Hackage link: http://hackage.haskell.org/package/blaze-builder All feedback is welcome, Kind regards, Jasper Van der Jeugt