Looks like David Hayden knocked out a “Twitter Bootstrap” theme for Orchard… Really looking forward to trying this one out. I might even update this site to run this theme, though I need to find out which versions it supports first. See more at http://www.davidhayden.me/blog/twitter-bootstrap-orchard-theme
I also found this Nuget package that contains an MVC3 template for Twitter Bootstrap, over here – https://nuget.org/packages/MahApps.Twitter.Bootstrap