Since 1997, Friedman has been continuing a series of posts to New York University's FOM (Foundations of Mathematics) mailing list which he calls the "numbered posts." They cover a wide range of topics in mathematical logic, and some of the research involves large numbers. For example, he discovered the block subsequence theorem, circle theorem, the TREE sequence, the subcubic graph numbers and transcendental integer. His finite promise games exceeds even Loader's function.
Friedman is also a self-taught amateur pianist.