japan-guide.com’s Japanese History is a quick guide through virtually any period of time in Japan.
American West has some unusual links – there’s even a Native Languages page – but it’s the page of Native American Nations homepages that’s invaluable.
And remember, Wikipedia has extensive links and essays on virtually any group – the basic summary page on Indigenous Peoples of the Americas alone contains dozens of links to other articles.
Stanford’s African Culture: Society on the Internet has an outstanding series of links on highly diverse subjects from textiles to philosophy.
History of China is text-heavy and useful historically, particularly regarding 19th and 20th century events through 1988. Academic Info has an extremely thorough list of links regarding China covering virtually any question you might come up with.
All Scandinavia is a rather painful primary color experience, but its articles are worth checking out, ranging from basic history (Who are the Scandinavians?) to the purely amusing (Norwegian drinking laws).
History & Culture of Russia is exactly what it says, in a neat, clear fashion. While by no means exhaustive, it’s a nice introduction. For a delightfully eclectic look at Russian culture, Alexander Palace Russian History Website has an exhaustive and unusual selection of websites that cover everything from books to building tours to jewels of the Romanovs.