So I was pleasantly surprised to discover () that sometime recently, Apple quietly updated the Store to provide just such an option. Now, when viewing an album that features song previews, there's a Preview All button that plays each track's 30-second preview in sequence.
Although the feature is still missing Amazon's handy buttons to skip to the previous or next track, here's a tip: while in Preview All mode, clicking iTunes's own Forward button, or pressing the right-arrow key on your keyboard, skips to the next track. (Oddly, although clicking the Back button or pressing the left-arrow key returns you to the beginning of the current track preview, clicking or pressing again skips you to the ' track, not the previous one.)
The feature hasn't yet made its way to the iTunes app on the iPhone and iPod touch.