Reviews of Japanese Job-Hunting Sites
When I was searching for my current job, I spent a lot of time scouring the Internet hoping to find a good position. Unfortunately, many Japanese companies never post open positions online, so searching online should not be your only option. That said, there are a few good sites (and many poor sites). I will briefly review the biggest players below.
I have ordered the sites by how helpful they were to me.
Daijob is my favorite of the job search sites, but they are heavy on senior level management positions. If you have the relevant qualification there are many intriguing opportunities. If you're just getting started in Japan, you should probably look elsewhere.
GaijinPot is a decent site; however, it caters primarily to English speakers. In some ways, this is good, but there is the bad side effect that many of the site's users speak very little Japanese. Because of this, when a company posts a job on the site, they are inundated with resumes from people who do not even qualify for the job. So, there are many companies which refuse to use Gaijinpot, reducing the quality of the site.
If you're looking for English teaching positions, though, this is your place.
Japan Career has a decent quarterly newsletter which you can download for free from their website. It has some helpful (though basic) information about finding work in Japan. Unfortunately, the job search functionality on their site is very limited, and they have few positions available. For awhile, they were recommending studying four years in Japan to graduate to a job at Lawson. I would take a look at their newsletters, but pass on the rest of their services.
JAC is a firm that has been hit hard by the recession. I had just talked to a recruiter in April of 2009 when three weeks later he sent me an e-mail saying he was losing his job and that JAC would be unable to help me. Two other friends had the same experience. At this time, I cannot recommend them.
Hello Work is the job search institution funded by the Japanese government. I experienced nothing but frustration working with them. In May of 2009, I visited a local (for Japanese) agency in the prefecture I was living, and the one especially for foreigners (in Roppongi, Tokyo). The Tokyo facility is nice because they have a list of jobs specifically for foreigners; however, the list is usually about 30 oddball jobs in the greater Tokyo area and that's it. It's certainly not worth a trip to Tokyo if you're not in the area.
Other Sites to Try
I didn't spend a significant length of time using any of these sites personally, but friends and visitors have recommended them.