Are consumer research companies who offer free merchandise as a reward
for my evaluation of products trustworthy?  Consumer Research
Corporation Inc. of Columbia, S.C. is an example, but there are many.
What can you tell me?

Hello oldhag-ga,

Many are reputable and useful companies. The company that you
suggested however is NOT (please note that is my direct opinion based
on research I have done about them).

A quick search on the internet came up with many disappointed people
who felt the company was not meeting its promises:
://www.google.com/search?hl=en&lr=&rls=GGLJ,GGLJ:2006-10,GGLJ:en&q=+site:www.ripoffreport.com+Consumer+Research+Corporation+Inc.

Some points that you should be aware of when you choose which
companies to participate with:
A) If you have to pay anything, start running.
B) Make sure that it is clear what you will be getting for your participation. 
C) Do some quick searches on the company itself to see what others think of it. 
D) If it seems too good to be true, it probably is. 

While there are several good companies out there, the problem is that
you will end up putting in more time than it is probably worth it for
you. The reason the rewards are so low is because so many people are
willing to participate (simple supply and demand).

A few reputable companies to get you started (again my opinion only): 

http://www.greenfieldonline.com (Not everyone gets the prize, they do
draws but if you win it is more significant, sort of like a free
lottery).

http://www.pineconeresearch.com/ (This is one I currently participate
in, they do not have open membership at this time but they open up
membership once in a while. They pay cash for every survey you
complete and provide you with product samples that you may keep after
reviewing it intensively).

http://www.memolink.com/ (They have surveys which earn points that can
be redeemed).

http://www.npdor.com/

Search Strategy:

site:www.ripoffreport.com Consumer Research Corporation Inc.

I echo the above post, pinecone research is indeed very reputable,
I've made about $50 from them in the last year, but I've made over
$300 from survey savvy.  Here's a link and screenshot of my account

http://www.imagedump.com/index.cgi?pick=get&tp=432221

http://www.surveysavvy.com/ss/ss_index.php?id=2011350&action=join