This isn't a start-from-Mārcus-puer-est resource, but Daniel Pettersson's website Latīnitium is designed to be a resource for people teaching themselves Latin on their own. It has articles in English and in Latin, really well-done videos and a podcast in Latin, and links to lots of other resources helpful for auto-didacts. He's among the most accomplished Latin speakers in the world, and I find the site incredibly helpful.

Latīnitium isn't the only Latin podcast: There's also Quōmodo Dīcitur, put out by Justin Slocum Bailey, Jason Slanga, and Gus Grissom, and Sermō Rædārius, by Alexandro Conti; I know of a few others in the works as well, which I'll come back and add when they come out.