Suprised that setting up a mailing list is any kind of hurdle.
But maybe the people I know are skewed toward those who run their own servers.
One way to get a mailing list is to use any of the forges (sourceforce.net, alioth.debian.org, savannah.nongnu.org). Just create a project for your event, put any custom code you develop in it. I doubt any of the forges would be against being used this way. Oh, and this also gives you a bug tracker.
On wikis, there are some that can use real html. Mediawiki might not be your best choice. I might be biased. :)