Many federal agencies and scientific journals have websites that include press releases on recent scientific research.
These releases can be used as the basis for newswriting exercises.
The New England Journal of Medicine: www.nejm.org
The Journal of the American Medical Association: www.jama.com
The National Science Foundation: www.nsf.gov
The Centers for Disease Control: www.cdc.gov
The National Institutes of Health: www.nih.gov
The National Institute of Child Health and Human Development: www.nichd.nih.gov