The University of Utah offers a one-page primer on MRI and PET imaging.
The National Institute of Biomedical Imaging and Bioengineering offers separate sections addressing the interests of researchers, students and the general public. The site includes information about NIH initiatives in bioimaging, a list of symposia and workshops, news releases, and links to other bioimaging sites.
This site, a joint effort of the American College of Radiology and the Radiological Society of North America, provides basic information about what to expect when undergoing diagnostic radiology procedures, such as CT scans and MRIs.