I just did a "post mortem" interview on Portal: Prelude, the Mod of the Year Awards, and stuff with the folks at GamesModding.com. There's nothing really new if you followed the development of this blog from the start, but if you didn't and/or want to know a bit more about the hows and whys of this mod, you should pay them a visit.
The interview is right there.
There's some really interesting questions, like "What is the most surprising thing you discovered while making Portal: Prelude?" or "What do you wish you had known before starting making Portal: Prelude?". Kudos to them for asking uncommon and interesting questions.