International Journal of Radiation Oncology Biology Physics - Commonly known as the Red Journal in radiation therapy community because of the color of its cover, this journal is the official journal of the ASTRO (http://www.astro.org/), American Society for Therapeutic Radiology and Oncology. Papers in this journal are usually written by both medical physicists and medical oncologists/radiologists.
Medical Physics - Medical Physics is the scientific journal of the American Association of Physicists in Medicine. Calendar of Events in Medical Physics and Links to Abstracts of Articles available free.
PubMed - PubMed is the National Library of Medicine's search service that provides access to over 11 million citations in MEDLINE, PreMEDLINE, and other related databases, with links to participating online journals.
Radiotherapy and Oncology - The official journal of ESTRO (European Society for Therapeutic Radiology and Oncology). Similar to International Journal of Radiation Oncology Biology Physics except mostly authored by clinical researchers from Europe.