ePHOTOzine has a nice article on the rights of photographers, it caters for the UK and gives some hints for freelancers and hobbiests.
Regarding pictures of total strangers – candid shots taken in the street, say – no one in the UK has copyright on their face, and providing you take pictures from a public place, there are no laws covering the right of privacy of the public. Therefore, if you photograph a ‘streaker’ running down the high street, there is nothing they can do about it legally. The only time problems occur is if that picture is published and the accompanying text is defamatory – suggesting the person was drunk or on drugs, for example – in which case the subject can sue you for libel damages because in fact they were just having a good time.
A Downloadable Flyer has been created for the USA.