Grant Research

When an agency asks you to do grants research, what they are looking for are corporations and foundations that fund organizations with missions and programs similar to their own agency.  
There are many online resources you can use to find funding leads for an organization. Among them:

http://www.foundations.org/grantmakers.html

http://www.fdncenter.org

http://fundingopps2.cos.com/cgi-bin/search

http://www.artswire.org/Artswire/www/awtour/money/page6.html

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You can also visit a search engine or directory and type in certain keywords, such as:

corporate+giving

corporate+foundation

foundation+guidelines

 
You can also try looking for organizations on the Web with a similar focus, and seeing who their funders are (if they are listed on their Web site).

Some resources to help you:

Idealist

Guidestar

 
NOTE:
Do not EVER contact any corporation, foundation or other organization unless you have WRITTEN permission to do so from the agency sponsoring this type of opportunity.