Kenji Mishina Japanese Sword Polisher. Has polished Nihontô in the collection of the British royal family.
Grey Duffin Tsuba and Nihontô books
This site has supplies for the conservation of Nihontô (uchiko, chôji oil etc), plus supplies and services for restoration (e.g. tsuka wrapping, fittings, etc). Lots of Nihontô information here too.
David Pepin Many swords, fittings and other related items for sale. Site has interesting and informative articles about Nihontô and tsuba.
A site with swords etc. for sale and much information about Nihontô and other Japanese weapons and armour including tanegashima (Japanese matchlocks). Also includes a feature on the five koto schools and pictorial glossaries.
Robert Cole The "Shoshin" site is very extensive with lots of reliable, detailed information, particularly about swordsmith lineage, as well as having swords for sale. Presentation is quirky though and you will need Adobe Acrobat reader software installed to access much of the material.
note that this list is for information only
Inclusion of a site does not imply recommendation