I use this website to test technical ideas and concepts that may make it to Flightfox. Some of it's for performance, some just for fun. See below for a list of the, albeit rudimentary, concepts tested.
Design
Perfect vertical rhythm of all sections, text and images
SVG logo that scales, no need for separate 'retina' images
Only using 'rem' units, no px, em or pt
Icon font for the little 'read more' icon
Fully responsive layout and high-DPI resolution friendly
Increased browser text-size and zoom friendly
Optimized CSS for EOT, SVG, TTF and WOFF font formats
Uses Open Sans font, including the condensed version for headings
Uses HTML5 elements, including datetime and pubdate attributes
Larger intro paragraph text
Performance
All content is static HTML
All resources gzipped and cached for 1 year (now hosted on GitHub)
Custom Nginx MIME types to gzip fonts (now hosted on GitHub)
Cache bursting in URI, opposed to query string
Minimal HTML5 markup, no compatability concessions
No Javascript, other than the Google Analytics snippit
All LessCSS files compiled into a single, minified file
Just For Fun
No ID or classes in CSS, all element selectors (I know, I know)
No Javascript, other than the Google Analytics snippit
To Do
Use a separate cookieless domain for assets
Build blog processor, minify HTML, make life easier
Microcache HTML pages with NGINX, maybe with Memcache
