This page will contain assorted information that I found useful. Corrections, suggestions and improvements can be mailed to firstname.lastname@example.org.
A note on armor contributed by Chris Bertani: Japanese armor started out as lots of little metal scales laced together, evolved into horizontal metal strips laced together, and eventually into solid plates, so it wasn't due to a specific style of fighting, unless of course styles changed, which they did. For instance, the oldest armors are designed so that the big flat shoulder guards fall back for archery. As archery became less important, the shoulder guards became smaller and more form-fitting. They did use mail on the sleeves ('sode'?) but not elsewhere, as far as I know. The lacquer on armor was an attempt at rustproofing, I think, and it looks cool, too.
Mike Ellis mentioned that the different clans reminded him of different periods in Japanese history, so I asked him to expand on that as a way of providing useful hints as to which parts of Japanese history to loot for ideas to use for a particular clan.
the emperor and rule the country' mentality and their code of Bushido. They're also the most uptight about the caste system.
The Lions are more like the Heian period--the court is the center of culture, and the warriors are there to support the court. The only real problem with this is that there wasn't a lot of fighting going on during the Heian period.
The Crab are like the Minamoto family of the early Kamakura: rough country warriors who admire the civility of their more cultured enemies while doing their best to wrest control of the country from them at the same time. (See the 'Tales of the Heike'. This makes the Crane the Taira family.)
The Dragons are of course the traditional Buddhist Warrior Monks, and so belong more to the Muromachi period where Zen was spreading through the country at the same time it was engulfed by civil wars, making strong, isolated mountain strongholds a necessity.
The Scorpion also belong more to the Muromachi, although I don't see them as having a true historical analog. They're opportunists, and there's opportunity in civil war.
I see the Phoenix as being perhaps linked to the Nara and Heian periods, the 'Golden Age' of Japan, although that period predated the whole samurai culture by a good time.
The Unicorn are just bizarre. Call them the various daimyo who were influenced by portugese and dutch missionares, traders, and explorers in the late Muromachi and Momoyama periods.
Once you get past the Tokugawa era you're into the Meiji, the emperor's back in control, and guns, cannon, and everything else is back in country. This would be bad for L5R.