Floor15 is a community site for bloggers. In the near future you'll be able to get your blog rated by other members, and rate other blogs.
"Floor": if you're part of an open forum, a topic might be thrown out "to the floor".
The number 15 will become a bit more relevant as we introduce new features to the site.
Other than that, there isn't a special reason for choosing this domain name.
It was available.
It's short.
And I liked the sound of it :)
Floor15 is a project created and maintained by Ben Barden. Some of Ben's blogs are listed below.