The Strokes, Is This It - everything, from the classic front cover to the black and white pictures of the band inside, just screams classic. They really jerked one of the park with that one.
Hope of the States, The Lost Riots. The effort that went into that, with all the beautiful illustrations - that still stands out as such a lovely thing.
More recently, I'd plump for the Vampire Weekend album. Something about it just really works on an aesthetic level, even if the inlay does smell a bit funny.