Apple have added official Photoshop and Sketch templates for quickly and accurately designing iOS apps to the iOS Human Interface Guidelines. Resources like this were famously built by Teehan+Lax in the early days of iOS, followed by Sketch shipping with bundled templates. Apple doing this officially is great to see.
Susan Kare is a design legend; although she's too humble to admit it. You should know her by name, but you will certainly recognise her work. Responsible for much of the early '80s typography and icon design on the Macintosh, this talk and the subsequent interview only brush the surface of the fundamental thinking and decision-making that led to the Mac—and graphical user interfaces in general—being something we now take for granted.
Espresso—long appearing to be abandonware—was one of my all-time favourite Mac apps. Although low on features compared to modern text editors, the features it does have favour front-end developers and the attention to detail is unmatched. The first public beta has some rough edges but I am very happy to see this one resurface.