Archival. Please see https://github.com/aleron75/mageres for the most up-to-date list.

magento-resources

http://alanstorm.com/category/magento
http://aschroder.com/category/magento/
http://blog.belvg.com/tag/magento-certification
http://demacmedia.com/category/magento-commerce/
http://ecomdev.org/
http://eschrade.com/page/category/magento-2/
http://inchoo.net/
http://www.nicksays.co.uk/magento/
http://www.excellencemagentoblog.com/
http://fabrizio-branca.de/magento.html
http://fishpig.co.uk/magento/tutorials/
https://gist.github.com/parhamr/6177160
https://github.com/colinmollenhour/
https://github.com/netz98/n98-magerun
https://github.com/rgranadino/Interactive-Magento-Console
http://magebase.com/
http://magedevguide.com/
http://magestudyguide.com/
http://magento-quickies.tumblr.com/
http://magento.stackexchange.com/
http://magentocommerce.com/certification/moderators-kit
http://magentocommerce.com/knowledge-base/entry/magento-for-dev-part-1-introduction-to-magento
http://magentocommerce.com/resources/magento-user-guide
http://magentocommerce.com/whitepaper/
http://nexcess.net/magento-best-practices-whitepaper
http://stackoverflow.com/questions/tagged/magento*
http://tweetorials.tumblr.com/
http://twitter.com/
@alanstorm
@benmarks
@IvanChepurnyi
@monocat
@vinaikopp

"Scaling Magento" Presented at MagentoLive UK 2013