I know there's one for sure in Terminal 2 (past security) just down from the Duty Free. IIRC theres also a non-club shower facility near the Yahoo Internet cafe as well.

Yahoo isn't the only internet service. But it is the only free one.

I haven't been to Terminal 1 in some time, I have a vauge recallection of security being a slight hassle compared to Terminal 2 if you wanted to visit any of the shops.

NRT has a very detailed web site in English about the airport and terminal setup.