Here's a great talk from the eminent neurologist V.S. Ramachandran. In it he talks about three fascinating phenomena: phantom pain; synaesthesia; the Capgras delusion (a truly weird, and very rare, disorder where the sufferer, although recognizing familiar people, believes they have been replaced with imposters -- this is actually a disorder of the face-processing software rather than, as it might seem, some sort of paranoia).

Don't miss the wacky way Ramachandran disappeared phantom pain in a sufferer! The human brain truly is an amazingly crazy, yet bizarrely logical, construction.