hi,
Is wiki the best platform currently [*hides from Ward*]? Is the software/configuration used by (I think) PLOS for a similar thing available somewhere to build on?
as mentioned previously, Open Journal Systems is popular http://pkp.sfu.ca/?q=ojs PLOS bases on Ambra http://www.ambraproject.org/ which looks decent, too, but I've never used it.
OJS is quite decent in managing the review process, using templates, etc. Not as decent as Manuscript Central, but open, and good enough. Ambra may be even better, maybe somebody used to edit in both and can comment.
But seriously, starting a journal is not so much about the engine, but more about the community to drive it. It wouldn't be unprecedented to start a journal by preparing 1-2 issues WITHOUT a system to process submissions at all.
best,
dj