My first big web application development project was building a complete Content Management System... from scratch. (At the time, an open-source CMS was unavailable.) I was extremely limited by the host, and the client was unwilling to change hosts, so we were forced to run everything off of a Microsoft Access database file using ASP. There were days where I was literally screaming at my monitor, trying to get this lousy getup to work.
My client was The Rock, a contemporary church, who I also did the web design for.
I called the CMS Insight, and even gave it a trendy interface. In both concept and practice, it worked rather well. But because it ran ASP with MS Access, it wasn't very scalable, and eventually it fell by the wayside.
This is one of my bigger accomplishments. A system this complex built on such limited technology was a major feat, and I'm very proud of the work I did on it. If anything, I became truly hooked on CMS concepts, and this paved the way for much of my work today.