Google Testing is a must-read for any serious software developer who cares about code maintainability, and what is considered best practice in the industry. I found the blog via their post on testing doubles, and highly recommend following going through "Testing on the Toilet".
Cal Newport is a Dartmouth and MIT graduate who lately became an assistant professor in Computer Science at Georgetown University. I've found his Straight-A post series to be an inspiring condensation of educational common sense, and his driving philosophy that "mastery leads to passion" a gem to keep life in perspective.
Joel on Software is much lauded and you will often find him referenced elsewhere on the Internet. His post on 12 Steps to Better Code is a must-read. The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) is something you will eventually read, no matter what you think now.
Martin Fowler writes excellent posts on software design, Agile development, code refactoring, and NoSQL.
42Go Engineering always writes crazy interesting posts for Scala developers.
JOOQ offers neat perspectives on SQL practices.