After the initial success of the J-league in the 90s there was enough interest among other amateur football clubs across Japan for entering the professional ranks that the J-League expanded to include a 2nd Division of 10 teams.
As time went on the club finishing bottom of J2 didn’t find themselves relegated, rather clubs wanting to join the league from the 3rd tier (the JFL) could do so upon fulfilling certain requirements expanding J2 to it’s current status of having 19 teams.
This odd number is less than ideal as it means one club won’t play every week, and there are intentions to allow entry to another 3 teams to make a total of 22 (2011), at which point it will start to be possible to relegate/promote between J2 and the JFL.
It is already possible to promote between J1 and J2, with 3 teams switching position each season. There is no play-off system at present, with just the top 3 clubs going up each season.
From this page I will link to information on the other 18 clubs in the division, and try to provide outside links to English fan pages for each of these clubs where possible.
If you run a fan-site which I have missed please contact me and I will add it.