Some parents choose to hire babysitters who speak a foreign language and require the babysitter to communicate with the child in that language so that the child can learn. I think this is a great option for parents who don't speak a foreign language or who don't have the time to teach their children themselves.
I also think that movies are a great way to learn a new language. I personally learned a foreign language this way, by watching movies in that language with English subtitles. So selecting children's movies in another language is a very good option. Libraries and bookstores also have instructional children's DVDs for foreign languages.
I'm not sure what the availability is, but another option could be a kindergarten which has a foreign language class as part of the curriculum. If you were already planning to send your child to kindergarten or some other preschool, that might be the best option for teaching children a second language.