https://github.com/varnish/varnish-devicedetect/
Simple regexes to handle device detection within varnish. Includes links to documentation and suggested implementations. Neat.
http://www.quirksmode.org/blog/archives/2010/09/combining_meta.html
Nerdtastic article on using meta tags and CSS to optimise site widths for mobile devices. Delves into a vastly deep amount of detail that explains why a simple principle will usually work. Useful.
