My eyelids are the only shutters I need.
Some shade too I assume? I find I at least need to ensure that my eyelids aren't subject to direct sunlight for sleep to be realistic. This occurs sometimes in my room when the sun is at exactly the right point and the curtains aren't carefully aligned. If I am trying to go to sleep at that time I need to either lie on my side such that my head is facing away or cover my eyes with a pillow (or be very tired, or it could be overcast).
Listening to heavy metal in a brightly lit room will almost inevitably put me to sleep within 30 minutes. One of my friends only produces melatonin when exposed to sunlight or full-spectrum bulbs. Not everyone's body responds to "night = sleep, light = awake".
I have often benefited from recommendations for Things I Didn't Know I Wanted.
Given that Less Wrong is a community of unusually intelligent, critical, and self-improvement-focused people, I suspect we can generate a pretty helpful thread of product recommendations — perhaps even a monthly thread of product recommendations.
Rules: