Building on the strength of LINQ to SQL, this release now includes support for multiple blogs using a single installation. This beta release is to get the code into the hands of hardy individuals who'll help me beat it up a bit.
See the Readme.html for configuration information including how to use the SQL Server scripts to create new blogs.
NOTE: IIS 7 will need to be configured as "Classic" instead of "Integrated". This is due to the fact that BlogEngine.Net ties into the application start event to load extensions (which, since it hits the database, also triggers a query for the blog id which uses the HttpContext.Request object to figure out which blog id to serve).