I found this article last weekend in SF Chron to be entertaining and interesting:
http://www.sfgate.com/cgi-bin/articl...RG01MRNIR1.DTL
"Tokyo turnaround: Enjoying Japan's big city for little dough is easy"
When we were in Tokyo almost a year ago we found a visit to Tsukiji Fish Market to be a great use of time, plus we had really good sushi there.