Listed below are several journals for undergraduates which are accepting submissions from all campuses:

Interdisciplinary:
Journal of Young Investigators
http://www.jyi.org
Online peer-reviewed national journal of undergraduate research.

National Undergraduate Clearinghouse
http://clearinghouse.mwsc.edu/default.asp
Accepts manuscripts from all disciplines for online publishing

Pittsburgh Undergraduate Review
http://www.honorscollege.pitt.edu/~pur/
A multidisciplinary and professionally refereed academic journal dedicated specifically to publishing original undergraduate scholarship.

General Sciences:
Caltech Undergraduate Research Journal
http://www.curj.caltech.edu
Online journal accepting submissions from undergraduate students at all institutions.

Department of Energy, Journal of Undergraduate Research
http://www.scied.science.doe.gov/scied/jur.html

Journal of Undergraduate Sciences
http://hcs.harvard.edu/~jus/home.html

Reviews in Undergraduate Research, International Journal of Excellence in Undergraduate Research
http://www.ruf.rice.edu/~rur/index.htm

Undergraduate Research Journal for the Human Sciences
http://www.kon.org/CFP/cfp_urjhs.html
An annual online national, reviewed journal dedicated to the publication of undergraduate student research

For Chemistry:
Journal of Undergraduate Chemistry Research
http://academics.vmi.edu/chemistry/announcing.htm

For Mathematics:
Furman University E Journal of Undergraduate Math
http://math.furman.edu/~mwoodard/fuejum/content/submission2.html

Morehead Electronic Journal of Applicable Mathematics
http://www.morehead-st.edu/colleges/science/math/mejam/tabofcon.htm

Rose-Hulman Institute of Technology, Undergraduate Math Journal
http://www.rose-hulman.edu/mathjournal/

For Medically Related Research:
McGill Journal of Medicine
http://www.med.mcgill.ca/mjm/authors/authors.htm
They publish student research ranging from basic laboratory science to clinical work to humanities analyses of medicine in society to medically related artwork.