American Research Group

This company conducts surveys for advertising and for political candidates and causes.

Cornell Institute for Social and Economic Research [CISER]

The collection includes federal or state censuses, files based on administrative records, public opinion surveys, economic and social data from national and international organizations, and studies compiled by individual researchers.

Gallup

A name synonymous with polling, Gallup has been studying opinion preferences for over 70 years.  Political issues are only one area covered, along with social behavior such as basketball, personal weight issues and workplace satisfaction.

National Council on Public Polls

"The National Council on Public Polls (NCPP) is an association of polling organizations established in 1969. Its mission is to set the highest professional standards for public opinion pollsters, and to advance the understanding, among politicians, the media and general public, of how polls are conducted and how to interpret poll results."  [from the site] 

Pollster

This site is a compliation of polling services updated to reflect  polling data on the Obama administration.  There is also extensive data on the 2008 Presidental race along with elections for Senate, House and Governor.

Zogby International

Zogby tracks public opinion for business, non-profits, the public sector and political causes and campaigns.  Other areas not often associated with polling include mock juries.