UPDATE 04/16/2007:
This download has been replaced by the Community Server Addons v1.1 for .NET 2.0 download.
To use this DLL place a copy of it in the bin folder and add the following line to the end of the CSModules section of your communityserver.config file:
<add name = "WGBCSAddonCreateUser" type = "WGB.CommunityServer.Addons.CreateUser, WGB.CommunityServer.Addons" />
This addon will automatically set the "Theme" of a newly created account to be the same as that of the "Anonymous" account. The result is that the anonymous account will become the true site default theme as new user accounts will assume its theme rather than defaulting to the "default" theme.