I came to know of Mark Chu-Carroll's "Good Math, Bad Math" blog via a post in “Programming Musings”, the blog of José Antonio Ortega Ruiz. Mark writes mostly about mathematics, the theoretical foundations of programming, debunking bad use of mathematics in popular and not-so-popular media, etc.
I find many of Mark's articles very interesting to read, though many others go way over the top of my head. Some of his recent articles that I found really interesting include one that shows how absurd arithmetic with Roman numerals can be, one on Poincaré Conjecture, some in the “Friday Pathological Programming Language” series, one on zero, one on i, one on e, one on Φ, one on Ω, one on Π, one on continued fractions, etc. The old home for the GM/BM blog contains many more interesting and insightful articles on math and programming theory. What an amazing guy!