Melville House are really kicking seventeen brands of arse with their book covers these days (see here, for example). Here are the first eleven books in their International Crime series.
I absolutely love these. They work as a series, with the limited palette, bold shapes, unflashy (but attractive) type and big fields of solid colour common to all. But then each author also gets their own identity within the series. The Kurkovs play wittily (and Saul Bass-ily) with the dinner-suit/penguin association, and the Derek Raymonds are just brilliant, reminiscent of old Romek Marber crime novel covers for Penguin.
I could kiss this publisher.
UPDATE: Kelly Blair did the Jakob Arjouni covers, and Christopher King did the Derek Raymond covers.