At some universities it’s a requirement to do internships. But even if it isn’t you should always look out for them. They offer detailed insights into all possible fields in physics and it doesn’t hurt to have them on the CV.
1.) Have you ever thought about working at CERN? Even as student you have different opportunities. Take a look here: https://jobs.web.cern.ch/join-us/students.
2.) Fermilab offers internships for students: http://ed.fnal.gov/interns/.
3.) IAESTE: The International Association for the Exchange of Students for Technical Experience (IASTE) is a worldwide organisations. It focuses on the distribution of internships for students in science and technology in other countries. IAESTE has offices in over 80 different countries and over 4000 traineeships are exchanged each year. Take a look at their webpage http://www.iaeste.org/ for further information.
4.) The Italian national committee of IAPS is setting up a project called FERMI. It will provide an employment database for students and young professionals as well as internships for those interested. First information can be found here (in Italian).
5.) The NASA offers different opportunities for students, including internships, fellowships and scholarships. Look out for todays and future calls here.
6.) AIFS Study abroad not only offers semesters aborad but also internships, e.g. in London or Florence. Check it out: http://www.aifsabroad.com/internships/.
7.) Each summer, the Space Telescope Science Institute (STScI) brings about a dozen highly motivated college students to Baltimore, Maryland, for a Space Astronomy Summer Program (SASP). STScI is the scientific operations center for the Hubble Space Telescope and the future James Webb Space Telescope. The SAS Program runs from mid-June to mid-August, and is designed for upper division undergraduates with a strong interest in space-based astronomy, engineering, and public outreach.
8.) The Computer Science Department at ETH Zurich offers a new, exciting fellowship program that allows undergraduate and graduate students to obtain research experience during the summer months. Applications for the programme are open to students across the globe. The program is committed to increasing diversity in the computer science and related technical areas. For more information visit the website (Take a sneak peek into the “Professors about themselves” part!), or send an e-mail to: email@example.com.