While researching the robotic sculptures of Kenji Yanobe (previously) I stumbled across this remarkable, eye-popping collection of artists at the Yamamoto Gendai. Enjoy...
Japan's National Diet Library Gallery has been mentioned here before, but the Pink Tentacle blog came across some fantastic late Edo period illustrations in the NDL Gallery by Kurimoto Tanshu (栗本丹洲, 1756 - 1834). Apparently he was a doctor, but he seems to be better known for his hundreds of biological illustrations. Many are of sea creatures, but there are also quite a few other plants and animals. ranging from realistic renditions to bizarre creatures. A huge and varied collection, but all are equally fascinating.
The Match World Virtual Museum is dedicated to showcasing the best artwork from the ~25,000 matchbooks in the collection of the Japanese Match Manufacturers Association, including Foreign Matchbooks, Advertising on Matchbooks and various matchbook companies, all with decent, sized images available if you click on the thumbnail versions. Some really attractive stuff in here. Previously on Metafilter
The Museum of Fantastic Specimens is an online (virtual) museum of taxidermy specimens of imaginary creatures, all created by hand by Japanese artist Hajime Emoto. The museum itself can be difficult to navigate, as all the links are in Japanese, so the link in this post goes to an unrelated overview page in English.
The Japanese Gallery of Psychiatric Art. Images from Japanese psychiatric medication advertisements: 1956-2003 (via Absent without leave)
The Kamagasaki Gallery. Background to and photographs of a Japanese slum.