Hello bharats,
I don't know what you mean by winter term, and I also don't know your location, citizenship, student status, or area of interest, but I thought these links may help you. Good luck!
Year-round internships:
Sandia National Labs Physical Sciences Institute (PSI)
http://education.ca.sandia.gov/internships/institutes/psi.html
Federal Bureau of Investigation (FBI) Counterterrorism/Forensic Science Research Unit
http://see.orau.org/ProgramDescription.aspx?Program=10063
NASA Education Associates Program
http://server-mpo.arc.nasa.gov/Services/eap/About/Program.tml
NSERC Northern Research Internships
http://www.nserc.gc.ca/sf_e.asp?nav=sfnav&lbi=nri
Most major companies hire student interns year-round.
Fall and Spring term:
Department of Energy (DOE) Science Undergraduate Laboratory Internships
http://www.scied.science.doe.gov/scied/ERULF/about.html
NASA Undergraduate Student Research Program (USRP)
http://www.vsgc.odu.edu/Menu3_1_3.htm
Oak Ridge National Laboratory (ORNL) Higher Education Research Experiences (HERE)
http://www.orau.gov/hereatornl/
Oak Ridge National Laboratory (ORNL) National Energy Technology Laboratory Professional Internship Program
http://www.orau.gov/orise/edu/NETL/NETL_PIP_app.pdf
Fall and Winter term:
National Science Academies Science & Tech. Policy Graduate Fellowship Program
http://www7.nationalacademies.org/policyfellows/
All gotten from the physics Student Opportunities listing at
http://www.astromiror.org/opportunities.html .