I think Chromium is definitely one of the best and most useful Open Source Projects, because so many modern technologies are based on it:

- Chrome + Chromium Browser
- Electron (Which is in my opinion the future of software development, as long as Web Apps don't have that many possibilities)
- Android WebViews
- Chrome OS (and Chromium OS)
- Many other Browsers like Opera, Samsung Mobile Browser, Vivaldi…

I think without Chromium the Internet wouldn't be the same today. It helped to popularize WebApps and helped to set many modern web Standards. Also, in addition with V8 it paved the way for modern JavaScript, as it provided (and still provides) developers and so also users with massive performance boosts.