Every morning, when I first log into the computer, I take a moment to write down what I remember from last night's dream. Some days, I can only write down the vaguest sentence about my dream. Other days I can write whole paragraphs of what happened, so vivid were the details. And still some days (most days), I report that I cannot remember a thing.
I can pinpoint when I began this habit: April 2011, with a Kickstarter ad for "Oneironautics: A Field Guide to Lucid Dreaming". This book attempts to teach you how to "wake up" inside your dream. One of the techniques for such "lucid dreaming" is to write down your dreams, building up a diary of your subconscious mind that you can study when you're awake.
I remember feeling this same excitement after watching the Richard Linklater movie "Waking Life", although at the time (early 2000s) I didn't realize there was a vocabulary for this idea. Of course, the recent movie "Inception" continued to stoke my interest.
As I reread a few of my own dream entries, I see the usual psychological debris of my past (college, high school) mixed with the racy and the rowdy. I sometimes think these dreams would make great movies, if only some screenwriter would make them half-way coherent. Until then, my dreams will just have to serve as my morning writing prompt.
For more on lucid dreaming, check out Dream Labs.