I would say there three major projects in my life.
I made davesite.com because (a) my family did not have enough money to buy me a car for my 16-th birthday and (b) high school is really boring. This project, which I had to learn HTML overnight for, ended up having more than 35 million visitors, and I estimate that from the authorized site alone, I taught about a million people to code. The site has been "pirated" tens of thousands of times, so I believe in the English speaking world, this course has probably taught a minimum of three million people. It also grossed more than six figures from Google's advertising program alone. Not bad for a science fair project.
The Cancer Game was an idea I had in 1998 when I had just a Palm Pilot (an early precursor to the iPhone and Android, minus the phone, minus the Internet. It had apps and a calculator.)
I figured, we could use a video game to influence cancer patients, resulting in them having better treatments. This was funded part by my college at the time, and part by a $1200 software donation from Macromedia/Adobe, who responded to my short e-mail saying, "Dave, tell us where to mail the software, and send us a copy when you're done." Thank you, Macromedia/Adobe.
I presented basic theory on this at The National Conferences for Undergraduate Research, but for legal reasons, I was advised to not continue writing about it, as a game that can "help" someone get better can also "hurt" someone. Legally. CRAZY!
I joke with this terminology. We can build beautiful buildings with architecture, so, if you build a beautiful, entertaining alternate reality game world, you're building argitexture. Argitexture, as I am now defining, is the intentional design of specific parts of an alternate reality game overlaying what a designer would call "Real life" or the "Real world." I'm writing a follow-up book to an argitexture project I built into my web site since 1996.