Quirks Market Research
http://www.quirks.com
Leading market research site and directory. Great for finding focus group facilities and searching for articles on a variety of topics.
Angoss Software
http://www.angoss.com/
A powerful software tool for segmentation and modeling.
Strategic Business Solutions, Inc. 
Nielsen - Claritas
http://en-us.nielsen.com/tab/product_families/nielsen_claritas
A national source for market demographics and household segmentation.
Info USA
http://www.infousa.com/
A national resource for consumer and business lists.
Tableau
http://www.tableausoftware.com/
A powerful tool for data analysis and visualization.