It's always been a big annoyance that when I go to http://www.google.com it often redirects to http://www.google.co.jp based on my IP address.
The problem with Google Japan site is that it puts priority on results that are in Japan. I usually want US-based results.
Anyway, I found an excellent post here:
Basically, just add an "hl" language parameter as follows:
"Within Japan" looks like a great blog overall for us techie gaijin living in Japan.