The word "recent" in the title may be a bit of a misnomer. I'm thinking of the influences that led me to make Mord Mar. All of them are from the past two years, and all of them have contributed something. In no particular order:
Undermountain: This was my first mega dungeon experience, and still colors my view of Dungeons and Dragons (and other FRPGs) to this day. My cousin still occasionally runs Undermountain when I need a break, and my Dwarf Druid is stupid powerful. (Powerful meaning able to run away succesfully).
300: I really think this movie is why Mord Mar was overrun by a terrible army. The visuals and fight scenes amaze me still.
Gary Gygax: When there is an unresolved rules dispute at my table, we go to the 1st edition books and read what Gary had to say. That's generally the final word. He created the genre, and even the megadungeon itself. I hope 5E gets closer to his vision than the last few versions were. And I hope they have the OGL back.
Castle of the Mad Archmage: I now have 2 copies of this masterpiece, the OSRIC and the Pathfinder versions. It is great. I look to it for layout of the dungeon in particular. I hope to have a chance to play in it someday.
Frank Mentzer's Lich Dungeon: He has some great ideas, that I'm not going to give away. Check out his work. I hope to borrow some concepts from him.
Conan the Barbarian: Probably the quintessential sword and sorcery movie. I love it, and it colors how I see combat in Mord Mar.
The Wheel of Time: I know a lot of people that say R.J. is a hack,but his interpersonal relationships are top notch. His attention to detail can get a little long winded, and that's something I keep in mind when writing descriptions of my own.
True Dungeon: This event allows me the perspective of seeing inside the dungeon. I get to see what it looks like from a character's and a player's point of view. Plus, Jeff comes up with some fantastic puzzles and creatures.