I discovered this hint completely by accident the other day. It is quite elementary, but many people, like myself, just might not have thought of it.
I always have the Browse window (View » Show Browser) open in iTunes, and use it quite frequently to find a certain artist I get a hankering to listen to. On one such occasion, I only wanted to listen to two out of the six CDs of one artist. Without thinking, I pressed the Command key and selected the two albums, and iTunes effortlessly added both albums to the list of things to be played (below the Browser).
Pretty simple, I know, but it keeps me from having to create temporary playlists whenever I want to listen to only two or so albums of an artist.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070422002322409