It is the first of January, so works from 1929 are now public domain in the United States. Here are some of them.
The Skeleton Dance, drawn by Ub Iwerks, music by Carl Stalling.
The Cocoanuts, the first Marx Brothers film (not counting an earlier unreleased silent film).
“Ain’t Misbehavin’,” by Andy Razaf, Fats Waller, Harry Brooks. (Only the composition is public domain, not this particular recording, which is from 1943. But hey, any chance to play a clip from Stormy Weather is a good one.)
“Rhapsody in Blue,” performed by Paul Whiteman and His Orchestra. (As a sound recording – the composition, by George Gershwin, was already public domain.)
The Treachery of Images, by René Magritte.
The earliest “Thimble Theaters” comics featuring Popeye the Sailor.
A Farewell to Arms, by Ernest Hemingway
And many, many other works, which you can read about here. Happy Public Domain Day!