Just scanned the Working and studying in Japan section, and noticed that the largest souce of teaching jobs in Japan is not mentioned. The free newsletter O-Hayo Sensei reports more currently available positions than the other publications you mentioned, combined (and has been doing so for the last 15 years). I don't want to make this sound too much like an advertisement, so I'll just give you the FTP address to download the current edition and check for yourself:
ftp://ftp.ohayosensei.com/current.txt