Energy Bulletin is a HUGE site with tens of thousands of pages and many, many daily visitors. I didn't create this site, but I took over maintenance and development a couple of years back.
I started by doing many overdue module and Drupal core updates, cleaning up the server and improving SEO by using proper 'friendly' URL aliases. Then I improved the site's performance and shunk the database from over 1Gb down to around 500Mb, and I also integrated the Disqus comment system and a Wibiya bar as requested. Later I added an "Editor's Picks" system and built them a more standards-complient and resilient theme which was based on - but enhanced - their previous look.
Recently I've manually patched their Mail Chimp module so it runs with the new API and built some lightboxes that ask for donations or show videos on initial arrival, and continue to provide support and advice.