There is no shortage of individuals and groups that help inform government agencies about S&T. Most federal agencies have advisory boards and committees that relate to S&T, which are made up, at least in part, by professional scientists and engineers. The challenge is to translate that advice into the best public policy decisions, which, of course, are influenced by factors that have little to do with science.
The President appoints his own advisory committee PCAST (see Department and Independent Agencies section for more details). Since all PCAST members serve "at the pleasure of the President", President Clinton had a different membership and chairs than President Bush, with two exceptions: Charles (Chuck) Vest, President of MIT, and Norman Augustine.
Another high-level advisory committee, that has substantial policy authority on NSF matters, is the National Science Board (NSB). The President appoints members of the NSB, but serve for terms of six years, with the possibility of reappointment. The intent of this statutory requirement is to keep politics out of science.
Most federal agencies have advisory committees (around 1000 in all) that relate to S&T matters. All federal advisory committees are subject to open-meeting rules specified by the Federal Advisory Committee Act (FACA).
The Federal government also receives advice on S&T matters from many non-government organizations (NGO), including: The National Academies of Science and Engineering, and the Institute of Medicine, the American Physical Society and the American Chemical Society (for a more through list see the relevant websites). The National Academies, through their operational organization, the National Research Council, are frequently asked by the Federal agencies, White House, Congress, and the research community to carry out studies on some aspect of S&T. Their voice is particularly important, since they use a rigorous review process to assure the integrity of their reports.
PCAST
President Clinton's PCASTState Department Science Advisor
Federal Advisory Committee Act: Website 1 or Website 2
American Association for the Advancement of Science