Litopia was by far the biggest of the three and was set up by my former agent, Peter Cox, as a kind of extension of his agency, but interfacing to the world through an open (and very large) forum for writers published and hopeful to get together, compare notes and generally support each other. As such, for several years it worked very well, and there are a range of writerly people around the world I now count as friends who I would not have met without it.
Unfortunately Litopia suffered from regular upheavals, some due to personality clashes with large egos involved, some due to misuse of the environment or to over-heavy moderation. In the end, there was an almighty row and it was 'temporarily' taken down. In a sense it was inevitable, as Peter, who largely funded the whole enterprise from his own pocket, had a different idea of what Litopia was for than most of those involved.
This take-down happened some while ago, but I am only commenting on it now because it seems clear that this temporary suspension has become permanent. Litopia isn't coming back. The good news for Litopians who miss their online friends is that there are ways to get together online still and many of the old faces regularly do - but I still think the passing of this worldwide meeting place is sad, a bit like an often-used pub closing down, and as such it is important to mark its passing.
A lot of people got a lot out of Litopia - for me it was mostly the social aspect, as writing can be an isolated business where you don't meet others doing the same job. For others it was a major boost to their writing, with free (if sometimes ferocious) criticism available of their works in progress. So farewell, Litopia. You started a lot of good things.
I ought to point out that Litopia's sister, Radio Litopia, a collection of podcasts and web-based broadcasts on writing and the wider communication world is still up and running and can be found here.