Derek Sivers is the personal website of entrepreneur Derek Sivers, founder of CD Baby, featuring short essays and book notes on business, music and living well.
Coding Horror is Jeff Atwood's blog about programming and software culture, written by a co-founder of Stack Overflow, with thoughtful essays for developers.
Daring Fireball is John Gruber's blog on Apple, technology and design, known for its commentary, link posts and the creation of the Markdown formatting syntax.
Seth's Blog is a daily blog by marketer and author Seth Godin, with short essays on marketing, leadership, creativity and ideas, famous for its brevity and consistency.