Before I got Calvin, I had read-up on bunny body language at http://www.muridae.com/rabbits/rabbittalk_intro.html. When Calvin is really interested in something or checking out the apartment before he starts zooming around, his ears are pointing forward. When he wants a good head rub, he'll hold his ears apart, giving me more "scalp" to rub, an action that the people at the shelter had never seen him do before when he did it on the day we first met and I brought him home. I call it the "Oh yeah, Mama, give me some lovin' " pose. His expressions are usually pretty simple since he's such an easy-going little guy and has no motives other than attention and getting good food.
Though Calvin is easy to read, Jessica is a whole 'nother ballgame. Her lop ears aren't as expressive as Calvin's "uppy" ears, but I've slowly learned to read her ears as well. When she's interested in something, they sort of slide foward like a pendulum, usually blocking her eye so she has to turn her head to the side to look at me. She's able to lift her ears up to half mast, as it were, when she is grooming, but otherwise they stay down. With the wide range of emotions and expressions she shows, her lop ears makes it harder for her to express herself so I can understand, so she adds the thump of a back foot for emphasis a lot. ;-)
It's not so much that rabbits don't communicate with us humans - we just have to learn how to listen and pay attention to them.