[godwine]

Make sure you spend sometime at Asakusa, Nakamise has some interesting shop selling traditional stuff. Tsuwabuki is right, Yokohama has a lot to offer, and can probably occupy you a day or so: Ramen Museum, Instant Noodle Museum, China Town, Minato Mirai and all the shopping

You can also spend a day or even 2 in Odaiba...... Harajuku is only about a few hours worth unless you want to drop by all the brand name store (LV, Gucci etc), Shinjuku is filled with shopping areas, I would be really careful around Kabukicho at night, or just completely avoid it... There are tones of interesting little stores in inner street. Shibuya, same thing, lots of inner street gems...