Synesthesia

1. SYNESTHESIA

The word "synesthesia" comes directly from the Greek (syn-) "union", and (aísthesis) "sensation", thus meaning something akin to "a union of the senses". Synesthesia is a neurological condition in which otherwise normal people experience the blending of two or more senses.  Synesthesia is additive; that is, it adds to the initial (primary) sensory perception, rather than replacing one perceptual mode for another.

http://home.comcast.net/~sean.day/index.html

2. GRAPHEME-COLOR SYNESTHESIA

The most common form of synesthesia is the association of specific colors with each letter or numerical digit; this is known as grapheme-color synesthesia. For example, someone with grapheme-color synesthesia might always perceive the number ‘2’ as being a “red number.”

http://www.macalester.edu/psychology/whathap/UBNRP/gcsynesthesia/introduction.html

3. ORDINAL-LINGUISTIC PERSONIFICATION

Ordinal-linguistic personification (OLP, or personification for short) is a form of synesthesia in which ordered sequences, such as ordinal numbers, days, months and letters are associated with personalities.

http://www.worldlingo.com/ma/enwiki/en/Ordinal_linguistic_personification#CITEREFSimnerHubbard2006

4. NUMBER-FORM SYNESTHESIA

A number form is a mental map of numbers, which automatically and involuntarily appears whenever someone who experiences number-forms thinks of numbers. In particular, it has been suggested that number-forms are a result of "cross-activation" between regions of the parietal lobe that are involved in numerical cognition and spatial cognition

http://www.synesthesiaweb.com/synesthesia_-_Various_forms_-_Number_form_synesthesia.htm

5. SOUND-COLOR SYNESTHESIA

This type of synesthesia is when individuals experience colors as a response to hearing music or sounds. 

http://undacovabear.wordpress.com/2009/02/08/sound-colour-synesthesia/

6. LEXICAL-GUSTATORY SYNESTHESIA

People who experience this have a rare condition known every word comes with an appended taste. For some, even when the exact word cannot be recalled, the taste of the word is there. It tends to experience the same taste for words with similar sounds.

http://www.newscientist.com/article/dn10644-think-of-a-concept-taste-it-on-your-tongue.html