Until only the last decade or so, we thought that cilia were organs of cell motility--period. But as I've noted in recent editions of my textbooks (e.g. Anatomy & Physiology, p.82-83), we now know that cilia play a critical role in a cell's ability to sense its surroundings.
Not only is this sensory function useful for, well, er, mediating senses such as hearing and equilibrium, it's also critical for cells to figure where to go (and when) during embryonic development. In fact, it's been shown that situs inversus (the condition in which internal organs are flipped in their left-right orientation) is caused by a mutation affecting the structure of the primary cilium of developing cells in the embryo.
Cilia, it turns out, are centrally involved in a lot of different cell functions.
If you want a quick and interesting review of the history of cilia from one of the pioneers in cilia research, including answers to "why do we have to learn this stuff if I'm going to be a [insert health profession here]?," then check out this article:
Eyelashes Up CloseFor more FREE images of cilia you can use in your course, see The A&P Professor website's FREE Image Library of Cell Structures.
The Scientist Volume 24 | Issue 7 | Page 30 2010-07-01
[Brief, well-illustrated review of what we know about cilia so far. Includes great graphics and useful references.]