The flagship of the chain is the massive Shibuya store that was first opened in 1976.
Tokyu hands is great because you can find virtually anything you are looking for. They carry countless products and many of these are only found in Japan.
You can buy basic hardware such as wood and paint, luggage, kitchen supplies, furniture, exercise equipment, toys, art supplies, costumes, pet supplies, storage products, lighting, home security systems ... this list goes on and on.
It is a interesting shop because it is a hardware shop targeted at the urban customer. Most DIY stores I have seen are targeted at the suburbs. Tokyu hands is haunted by a young crowd and is the essential store for any artist, musician or designer.
It is a very useful shop for anyone, the only downside is that the prices are not discounted and its a little on the expensive side.