I was the lead developer for this small adult media startup. I wrote a complete location-aware dating site backend, image processing tools, and a slick image viewer application, all on a standard LAMP stack. We had community features and single sign-on authentication when that was still comparatively rare in the adult space.
One part I'm particularly fond of was the query for retrieving profiles of people near a zipcode. It used the great-circle distance to find zipcode centers within a given latitude/longitude, with internal and external bounding boxes. Since bounding boxes are square, they can be used to implicitly include or exclude a set of points based on a concatenated index. Then, the expensive calculation only needs to happen for the small number of points outside the boxes. This was all accomplished using a single SQL query, on MySQL 3.23 (so, no subquery support).
I was also responsible for UI design and user experience testing, though I didn't do any of the graphic design.
My stuff worked great, but the company failed anyway. It was a good lesson in how great ideas and shiny technology won't get you far enough, you need good business practices and effective marketing to back them up.
You can still find bits of the site over on the Internet Archive.