If you already have contacts or a network abroad and you’ve made an internship connection already, you can participate in a self-organized internship. This is usually suitable for students who are comfortable working and living in the host country language and culture. You should expect to be fairly self-reliant: ie, able to secure your own housing and navigate around your host city. As long as the internship is at least 4 weeks long, you may be eligible for the C.V. Starr International Experiential Learning Fellowship
If you already have an internship offer but you need assistance with visa sponsorship, you can get help through the following services:
UK: BUNAC is the official internship visa sponsor for the UK. They can also act as a full provider, if you need more substantial help. Can also place in Canada, Australia and New Zealand.
France: The French-American Chamber of Commerce can sponsor a visa for a full-time temporary work position up to 18 months.