Monotaro is a great online hardware store. It could be compared to McMaster-Carr, but less easy to navigate (McMaster is almost entirely picture card driving. It is teh awesomes). The site is very google translate friendly as well.
Here are some select items, relevant to Tokyo HackerSpace, broken into categories which this author thinks are useful. Some of these are downright hints to our members to buy and donate them to the space. ;)