Computists International publishes a list of AI related jobs, which is 
also posted periodically to comp.ai at the request of the moderator. 
Computists International also publishes a set of informative newsletters 
that may be subscribed to at http://www.computists.com with membership.  
Student fees are (as of 3/30/00) $22.50 and professional fees are $47.50.

For neural networks, the Neuron Digest and Connectionists mailing
lists are a good source of job postings. For computer vision, the
VISION-LIST digest includes occasional job announcements. A good
source for general AI is Computists' Communique. For postdoctoral
appointments, see sci.research.postdocs.