Automattic is the WordPress shop. They develop WordPress and run WordPress.com. There aren't any recent revenue numbers available, but indirectly powering ~25% of the internet is nothing to sneeze at.
That's interesting; they really don't have the brand recognition they deserve then. I would consider myself as reasonably well-informed as the next HN reader, and I certainly hadn't heard of them. Of course I don't work with WordPress - but i have heard of WordPress...