MMM has done some articles where he's touched on Stoicism and Buddhism in regards to Mustachianism. I've seen a couple threads where people have mentioned Objectivism and other things Mustachianism reminds them of. I have a couple ideas that come to mind, like Epicurianism (avoid pain and embrace pleasure, but meaningful pleasure and not hedonism), Cynicism (the old school Cynics who believed in simple living, not modern complainypantsism), and Transcendentalism.
Kind of interested in if it reminds anyone else of anything, since I was into philosophy in high school and between some of what I read and my own personal background, reading the blog it felt like it "clicked" since I was familiar with the concepts.