I have grapheme-color, sound-color, and personality-color synesthesia. Basically it means that the nerves in my head are connected slightly differently than normally. I see lots of colors in my head--every number and letter has a different color, I see different colors of sounds (music is beautiful), and people each have their own color too.
Studies seem suggest that as many as 1 in 20 people have synesthesia (or has few as 1 in 20000). Most people who have it aren't really aware of the fact that they have it, I assumed that everybody saw the world the way I did until I read about the condition in my psychology class!
So are there any other nerdfighters with synesthesia?