Although it was made in 2009 and released on YouTube in early 2010, it's only recently that I've seen this short film by director Terri Timely entitled "Synesthesia" (via both kottke.org and laughingsquid.com).
Inspired by the neurological condition of the same name, Timley's film applies artistic license to the phenomenon of blended sensory perception. Not shown in the film is the most common form of synesthesia, in which letters and numbers are perceived directly and involuntarily to have an inherent coloration - for example, "A" might be purple (though research shows it's most frequently red). I've had the pleasure of teaching a student with synesthesia who had this type of perception; you can read and listen to the perspectives of two synesthetes (via MIT), and even see their colored alphabets.
Research on the areas of the brain involved with synesthesia is ongoing, with functional imaging studies and work with stroke patients serving as leading sources of information.