Working or studying at a summer camp may also be a way of improving our English, here you have some links:

Coordinadora d’organitzadors de camps de treball internacionals de Catalunya

http://www.cocat.org/cti.php

List of links of summer camps in UK

http://www.shambles.net/pages/Countries/uksummer/

Camp America: work in a summer camp in USA

http://www.campamerica.co.uk/