This is the the Haskell Platform, version 2009.2.0.1: a single, standard Haskell distribution for every system.
The Haskell Platform is a blessed library and tool suite for Haskell distilled from Hackage, along with installers for a wide variety of systems. The contents of the platform are specified here: Haskell: Batteries Included.
The platform saves you the task of picking and choosing the best Haskell libraries and tools to use for a task. Distro maintainers that support the Haskell Platform can be confident they’re fully supporting Haskell as the developers intend it. Developers targetting the platform can be confident they have a trusted base of code to work with.
It looks interesting; a blessed package collection and a compiler ready to run on OS X, Windows, and Linux.