Visit the airport !!

If you are willing to go land-side (and for 10 hours, you really should), you can take the monorail (paid) / bus (free) to the two domestic terminals at Haneda, where essentially one serves Japan Airlines (T1) and the other Air Nippon (T2). Both are a cultural throw-back and worth a visit, especially T1 which is the older of the two, and has many miniature versions of venerated Japanese shops such as Takashimaya.

All three terminals have sky decks, but the view from the 6/F sky deck of T1 is fantastic. It looks back towards the International Terminal, with Mt. Fuji as the backdrop :

http://www.star-telegram.com/news/bu...%20airport.jpg

The sun also sets behind Mt. Fuji, and if you get there on a clear day, the view would just be phenomenal.

As for lounges, both CX and JL have opened new J lounges in Haneda and are very much worth visiting. The JL one has showers.

HTH.