Website
I posted in this thread soon after it started and have been following it ever since. I don't have a direct Pentland connection, so I'm happy for the rest of you to make decisions on where/how to create a web presence, but I do have a bit of experience of websites etc.
First, Rootsweb is completely free, though pages have Ancestry banner ads. There are a number of options there: I think it's possible to upload a GEDCOM and have pages generated automatically (or has this facility now been transferred to Ancestry?), but my experience there is with Freepages, where any kind of FH site can be uploaded. You can see mine by clicking the globe on the left of this message.
Freepages sites can include guest books, but they are rather prone to spamming. For a while I tried having a blog for people to comment in, but there was very little interest (and a lot of spam to deal with) so I gave it up. Rootsweb don't host blogs, so this had to be elsewhere.
Another possibility would be to get some webspace, either free (with ads) or paid for. I have a personal site with Relichost for a very reasonable fee; I'm currently using it for a photo gallery, but I could if I wished upload a similar site to my Rootsweb one, and host a blog or mailing list or my own forum. phpgedview might be a possibility as well, but I haven't looked into it.
I've also read good reports of Tribal Pages, and I understand there are various options for public/private access.
I wonder if it might in the end come down to a combination of sites (at least to begin with, as experience might help in clarifying what is needed), depending on exactly how you see the project developing:
Is the tree to be a definitive one that is open to the public? If so, I suggest that one person only (and a reserve) has access to it, who will incorporate everyone else's research.
If it's to be a collaborative tree that anyone can work on, then the Tribal Pages approach might be good, but I don't know if TP includes any discussion tools as well.
Some kind of blog or forum seems to me a fairly essential part of the venture, either as part of the whole package or standalone. There are a number of collaborative web-based family tree packages available - Google brings up My Heritage, Geni and Famiva to name a few, and I've no doubt there will be many more - and it may be worth investigating how well these would fit the bill. Could someone do this, with the aim of producing a shortlist of definite options?
Arthur