Audiotapes, like books, remain among the least costly training tools in the market, costing about $12-$25 each.

Particularly effective for language and interpersonal skills training, audiotapes are ideal for employees who spend a lot of time in their cars or in travel. Look for tapes that include blank "airtime" for listeners to respond aloud, so learning can be less passive.

Of course, audiotapes fall short of real interactivity, and they may be an earful when covering complex subjects. It can also be hard to find much in the way of choice these days. The variety of training available on audiotape has dropped as flashier media become more popular.