Projects | iTunes Music Store Auto Play (Mac Only)
After downloading the script just drop it in your /Users/your-user-name/Library/iTunes/Scripts folder. Then, load up the iTunes music store and one-click the first track of an album (to highlight it). Next, use the iTunes script menu and select "MusicStoreAutoPlay" to begin playing that albums tracks.
Apple has finally added this functionality to the iTunes Store. You can read my thoughts on Apple's update in this blog post.