This is by no means a comprehensive list!  Instead it is a list of some of the big names in the industry ...  There are many more market research companies, and many focus on a particular industry.

If you need to find a company to do a particular type of research, try GreenBook (first link below).  Or if you need to find out if anyone has already done some research that you could use, try MarketResearch.com (second link below).

A list of segmentation systems from various vendors ... not comprehensive, of course!  Most of these links simply provide descriptions of the segments, and maybe some information about their development and methodology.  Two provide free ZIP code lookups (ESRI's Tapestry and Nielsen Claritas' PRIZM).

For some of them, there is data available within the Simmons NCS dataset ...

For the United States, an important source of data is the US Census Bureau, which produces a huge volume of data. It mostly uses the NAICS code to organize the industry data. (So if you're not sure what codes may apply to the industry you're researching, please click here.)  Below are links to the websites for many of the publications from the Census Bureau.

Again, this is not a comprehensive listing, just a sample ...