Here are the details (obvious spoilers if you are looking to avoid that sort of thing):
Hulbuster armor is featured with it said it's almost as big as the Hulk, with Iron Man fighting the Hulk.
Scarlet Witch is said to have mysterious reality-warping powers, with floating blocks shown.
Quicksilver was shown running.
Both Scarlet Witch and Quicksilver were shown locked in Perspex prison cells, as well as Scarlet Witch seen fighting alongside Hawkeye on the streets of Italy.
The Avengers Tower was featured, which is the rebuilt Stark Tower featuring: floor to ceiling windows, twin laboratories for Stark and Bruce Banner, and parking for supersonic jets; also described as similar to a S.H.I.E.L.D. helicarrier, with lots of shiny metal pillars.
The Guardians of the Galaxy footage also shown is said to feature Rocket Raccoon organizing a prison break, to the song "Hooked on a Feeling" by BJ Thomas.
(via Radio Times)
"Guardians of the Galaxy" blasts off August 1st.
"The Avengers: Age Of Ultron" hits May 1, 2015 directed by Joss Whedon starring Robert Downey Jr., Chris Evans, Chris Hemsworth, Scarlett Johansson, Mark Ruffalo, Jeremy Renner, Samuel L. Jackson, Elizabeth Olsen as Scarlet Witch, Aaron Taylor-Johnson as Quicksilver, Paul Bettany as Vision, with James Spader as Ultron.
Head on over to the Cosmic Book News Avengers movie hub for more.