IDSGN has a beautiful series of posts going on at the moment called 'know your type'.
So far they have Futura, Din(mmmm), Verlag(eurgh) and what is being dubbed "typeface of the century" Gotham. Each has great examples and details on the design and origins of each typeface. All good and worth checking out.
I'm hoping there will soon be posts on Avante Garde, Lubalin and the mighty Gill Sans.