Base UI Sketch Framework - Huge set of everything you need to design and prototype
YayText! - 𝓢𝓾𝓹𝓮𝓻 𝓬𝓸𝓸𝓵 𝓾𝓷𝓲𝓬𝓸𝓭𝓮 𝓽𝓮𝔁𝓽 𝓶𝓪𝓰𝓲𝓬
Framer Inventory 3 for Sketch - Import states & export prototypes from Sketch to Framer
Sketch Extensions - An official collection of Sketch extensions & plugins
Type Foundry Index - Making type foundries easy to find.
Flowkit - Sketch library for user flows/content maps/annotations