I said back in April that I was going to be working on a second edition of the Typeclassopedia. Since then I have worked on it some, but mostly I’ve dithered trying to work out a toolchain for publishing it in multiple formats including PDF and (commentable) HTML. But it’s become increasingly clear to me that this is really just getting in the way of the important work of actually updating the content, and I ought to just choose a simple solution, imperfect though it may be, and get on with it.
In the meantime, it turns out that Henk Krauss (geheimdienst) has been doing the tedious work of porting the Typeclassopedia to the Haskell wiki (thanks!). It looks much nicer than I thought possible for a wiki page, allaying one particular misgiving I had about publishing in wiki format. And this format obviously makes it extremely easy for others to contribute.
The path forward is clear: I hereby declare that the Haskell wiki version of the Typeclassopedia is now the official version, and from now on I will be focusing my efforts there. You can expect a bunch of updates, improvements, and expansions over the next few months. If you have any improvements to suggest, you can make them directly, or leave a comment on the talk page.