Gusto (formerly "ZenPayroll") is is a comprehensive HR, payroll, and benefits service enabling businesses to set up and run payroll from any web-enabled device.  The company changed names in order to show that they are hella-committed. 
Gusto was founded in 2011. The company's offices are in San Francisco and Denver.
Gusto has raised $157M to date. Investors include Google Capital, General Catalyst, Kleiner Perkins, and the founders of Instagram, Stripe, Nest, PayPal, Yelp, Dropbox, and Eventbrite, among others.