I'm not sure if this is new in iTunes 3, but it would make sense as there is now shuffle by album in the new version. To jump to the next album, simply click the next track button while holding down option. This also works for clicking the previous track button.
Maybe a less handy trick to go along--if you have the iTunes window somewhere where you can access it while in any app, and you want to switch albums but don't want to hide the app you're in (since holding down option will hide the application you're in), hold down control and option while clicking the buttons in the background and it will not hide the foreground application. This will, however, make iTunes the foreground application, whereas just clicking the next track button will go to the next track but leave iTunes in the background. If anyone has a solution for this, please post it!
[Editor's note: I'll admit I had a bit of trouble figuring out exactly how this works, and I'm still not sure I've got it. Open the iTunes Browser, select an artist on the left, and then view the song list window by album. Pressing Option and forward/back does, indeed, jump from album to album ... at least, when I'm in straight-play mode it does. When in shuffle mode, I couldn't really tell what it was doing; it seemed to jump back and forth between two albums until they were exhausted, and then switched to the next album ... odd but probably lack of understanding on my part. My normal use of iTunes involves launching and hitting Play on the Library in random mode!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20021014060138513