NameCheap is a popular, simple domain name registrar.
Mcmaster-Carr is a popular industrial distributor with a famously convenient website interface.
ULINE is a North American shipping supply distributor with a convenient ordering workflow.
Stripe is an online payment processing platform.
Protolabs is a rapid prototyping and on-demand production service for 3D printing, CNC machining, and injection molding. Based in Minnesota, US.
Youtube - General purpose video hosting. Immensely popular.
Vimeo - Video hosting aimed at professional, high-quality content.