Hi all, 

Where can I find information on characteristics and performance of
light materials (e.g., carbon fiber or plastics)?
I am trying to find a resource where I could learn more about these
materials’ weight, strength, stress factors, average cost (if
available), and other industrial characteristics.

Basic material information on the web can be found at:

www.machinedesign.com
(sub webpage in machinedesign.com for materials)
http://www.machinedesign.com/ASP/enggMaterial.asp?catId=372

However information about materials on the web is at best poor.  I
recommend a software program called:

Cambridge Engineering Selecter

With this software you can look up any material and get all the info
you need on it in a second.  The best part is that it can choose the
BEST material for you after you input all the constraints of the
material you desire.  Its somewhat like an optimization problem.

These books might also help:
MATERIAL SELECTION IN MECHANICAL DESIGN
ASHBY M. F.

MATERIALS AND PROCESS SELECTION CHARTS
ASHBY M. F.

ENGINEERING PLASTICS, VOLUME 2
ASM INTERNATIONAL

MATERIALS HANDBOOK
BRADY G. S., AND CLAUSER H. R.

I read a material science text, found it very helpful.  There is much
more to consider.  All materials have different strengths at different
temperatures, and there are a lot of options with regard to
composites.  Boron is a good material, but it weakens at high
temperatures.  Polymers (like plastic) also are strong, but weaken at
high temperatures.  In composites, the different elements react
differently when combined with different things.  Also, from an
engineering standpoint, it is important to consider "durability"
within its context.  differently alloys will react differently to
stress.  Aluminum is cheap for its strength, but will develope stress
fractures.  It is a decent conductor, but it is not often used for
wiring because its oxide is not conductive and this makes it very
unsafe to use this way.  You should consider the environment,
especially with metals.  Some of them corrode very badly.

Thanks saem_aero and stevenpace. The Cambridge Engineering Selecter 
seems to be just what I needed (though it is too technical).

Try the website www.engineering.com. There is a lot of useful
information on there, and membership is free.