(If you are new to MCU, then you should start with; Iron Man, The Incredible Hulk,
Iron Man 2, Thor, Captain America and then Agent Carter.)
Stark Expo 1974 - commercial for Stark Expo 1974 in Flushing Meadows in New York.
There are four different Stark Expo 2010 videos:
They take place during Iron Man 2 and you can easily find them by googling for them.
S.H.I.E.L.D spin-off mini-series Slingshot can be found at ABC's youtube channel.
Marvel Cinematic Universe (#1-4) tie-in comics :
[Last updated: Monday January 8 2018]
Marvel Cinematic Universe
This is the official viewing order for all movies and series in the Marvel Cinematic Universe
Webisodes (Most of them are at YouTube)
Comic Books and Graphic Novels that also follow the timeline: