Advocacy Groups, Interest Groups-a collection of individuals who seek joint ends through political action and tend to have narrow goals focused around an issue or issue area. These can be: private groups, sponsored by corporations, private industry; non-profit or citizens groups, e.g., AARP, Children's Defense Fund; labor groups. The organizations may conduct research or use others research to support position, provide policy briefings, etc.
The legislative section or "news alerts" area of the websites of advocacy groups can be useful sources for bills that are directly related to their mission.
How do I find advocacy groups?
You can try thinking more generally about trade or professional organizations that may be invested in a particular topic or bill, e.g., National Education Association, Children's Defense Fund, National Immigration Forum, American Academy of Pediatricians, etc.
Use Google to find advocacy organizations: Try searching your topic or legislation, limiting the search to site:org. For example, immigration site:org; no child left behind site:org. Or you can use phrases such as legislative action children, immigration advocacy groups, etc.
Committee reports are analyses and recommendations regarding legislation, and are very useful for ascertaining the purpose or intent of a bill. When the House and Senate cannot reconcile their different versions of a bill, a committee with members from both houses works out a compromise and issues a conference committee report.
"A hearing is a meeting or session of a Senate, House, joint, or special committee of Congress, usually open to the public, to obtain information and opinions on proposed legislation, conduct an investigation, or evaluate/oversee the activities of a government department or the implementation of a Federal law. In addition, hearings may also be purely exploratory in nature, providing testimony and data about topics of current interest. Most congressional hearings are published two months to two years after they are held." (GPO). The Government Printing Office prints the official, complete version, and not all hearings are published.