I have set up a page on the wiki for discussion:

http://www.haskell.org/haskellwiki/Haskell_and_mathematics/Hierarchy

And about a darcs repo for people to patch against:

---------- Forwarded message ----------
From: Simon Marlow < simonmarhaskell@gmail.com>
Date: 03-Apr-2007 20:28
Subject: Re: darcs.haskell.org access for maths hierarchy
To: Alexander McPhail < haskell.vivian.mcphail@gmail.com>

Hi there,

The plan is to set up a separate server for hosting community projects.  Right
now we have the server, but we still have to set it up.  Hopefully it should be
available soon, we'll announce something when it is.

Cheers,
        Simon

Alexander McPhail wrote:
> Hi,
>
> There is some movement on the haskell-cafe mailing list to set up a repo
> to develop a mathematically sound algebraic class hierarchy.  I have
> volunteered to coordinate this.
>
> What is the policy on giving access to darcs.haskell.org
> <http://darcs.haskell.org>?
> Cheers,
>
> Vivian
>
>