I've noticed that my favorite albums have a gentle "roller coaster" effect and that not all of the tracks have the exact same amount of loudness. The trick is to get them all in the same ballpark, paying attention to the feel of each cut. Listen closely to an album that you consider is good from start to finish and find the "money" cut, you'll probably notice that the song before it has a slower/mellower feel that may sound slightly lower in volume before the "money" jam comes on.

A good example that comes to mind (just listened to this yesterday) is Mos Def's "Black on Both Sides". If you listen to the track before "Ms. Fat Booty", called "Love", it has a smoother flavor and the level is just a tad bit softer that "Ms. Fat Booty". It feels like a prequel to a track that is more excited and I think this sort of effect makes listening to an album from beginning to end a better experience, so planning this sort of thing is cool if you want your listeners to listen to your album from start to finish. If the softer songs have a slightly lower average loudness, this is okay (as long as it's not obvious).