Episode 4 of Halo 4's Spartan Ops campaign is dropping today on Xbox Live. Like past episodes, all you need to do is boot up your game, go to Spartan Ops, and it'll automatically show up.
Make sure you play them in the most fun method possible: multiplayer on Legendary. In addition to Episode 4, an "FFA throwback" list has been added today, and includes Oddball and King of the Hill.
Mondays have basically become 343's Day to update everything, as the alleged dates for the map packs are slated for Mondays, Spartan Ops are released on Mondays, and according to 343 themselves, all exploit and glitch fixes will be patched on -- you got it -- Mondays.
As for myself, I need to catch up with Episode 3 first! The Wii U has been keeping me off Halo for a while, but I love how 343 has handled extra content with this model -- we can only hope for a Spartan Ops Season 2.