When I don't have access to blackout blinds, I find that eye masks have a similar positive impact on my sleep.
Dan mentioned a study highlighting the impact on light on the skin. I highly doubt that light on the skin has a significant impact on sleep, and my guess is that eye masks have almost an identical impact versus blinds. Of course, this requires that the mask doesn't allow light in or cause discomfort. You have to go for premium masks, but I think mine only cost about £15.
Like another commenter, I've found that exercise late in the day affects the depth of my sleep. I imagine it raises my cortisol levels as I just feel restless into the early hours of the morning.
I also find heavy or sweet foods in the evening to be a big issue. I tried apple cider vinegar after a recommendation from Tim Ferriss. It seemed to have an impact but I need to test it properly.