Here is an obviously non-exhaustive list of blogs, which would be of interest for someone working in machine learning:

• Cross Validated: http://stats.stackexchange.com (OK, it is not really blog, but rather a question-and-answer site. The answers, though, are often so good that they could be published as blog posts as well.)
• Machine Learning Theory: http://hunch.net. The average pace is one post per month, very practical, always surprising approaches
• Edwin Chen's Blog: http://blog.echen.me. The average pace is one post per month, covering more applied topics
• Machined Learnings: http://www.machinedlearnings.com. The average pace is one post per month, covering more applied topics
• FlowingData: http://flowingdata.com. The average pace is one post per day, with the posts centering on statistics
• Simply Statistics: http://simplystatistics.org. Several posts per month, focusing on statistics and big data
• Statistical Modeling, Causal Inference, and Social Science: http://andrewgelman.com. One post per day, often often funny reads when the author points out flaws in popular media, using statistics