I haven't gotten around to seeing all of his movies, I've seen personally, Warui yatsu hodo yoku nemuru (The bad sleep well), Maadadayo (spelled madadayo in English), as well as Yume (Dreams...)...
I would definitely recomend the Hamlet-inspired Warui yatsu hodo yoku nemuru, as well as Maadadayo (as long as you can excuse the fact that the movie is basically one big homage to by Kurosawa to himself), Dreams is made up of many different stories apparently based on the dreams of the director himeself, some work, others not so much, but it can have many different moments of beauty like much of Kurosawa's work.
Other films that are most likely to be mentioned when speaking of Kurosawa's most important work are...
Kakushi-toride no san-akunin (Hidden Fortress)
Rashouman (English title: Rashoman)
Shichinin no samurai (Seven Samurai)
Ran
Kagemusha
& Yojimbo.
He's also (uncredited) for the filming of the Japanese segments of the seminal film, Tora! Tora! Tora!... Tora! Tora! Tora! is a bit like reading a history book, you get to know what happened, but not a full understanding of why. The movie is practically devoid of emotion.
Still, it's fourthousand times better than the Ben Affleck vehicle movie "Pearl Harbor", so I guess you can choose your poison there.