I don't think Sandia policy would allow for a Wiki on lammps.sandia.gov. I
also don't think anyone will move the site elsewhere, which means a
stalemate with regards to your suggestion...
One possibility would be wikia.com, which is a site setup by the Wikipedia
folks to allow other people to create subject specific wikis. The nice
thing is that everything is already setup - all you have to do is go to
the site and register the new wiki.