I have been brought up in a multi-lingual environment and I consider it essential to raise my children the same way. I have done so by buying English, German, Dutch and French books. My idea is that if they are surrounded by enough reading material, the learning of multiple languages will come naturally. I have no proof for this assumption and it is my gut feeling. We now have some really nice german children books bought on the German amazon, although we both don't speak german. Now that they start watching tv, I was looking for children shows on Youtube. It appeared to be more difficult then with books. There is of course teletubbies or bumba on youtube. Since there are people from multiple cultural backgrouds here, I was thinking of posing the question here to suggest nice children episodes here.
I'm sorry but I don't think that just buying foreign books on Amazon is going to help a lot. It's just as difficult for a kid to simply pick up book in a foreign language and make sense of it as it is for an adult. As the parent, how are you going to support that learning when you yourself don't speak that language?
The same goes for other medias like YouTube or DVDs, though perhaps to a lesser degree. I believe that material like comics such as Donald Duck, or tv shows such as Sesame Street and Muppet Show, would be your best choice because these things are very visual and therefore work well without understanding the language.
But studies suggest (see references below) that children don't learn well on their own from a screen. What's lacking is the interaction and the actual presence of a real human -- and for language learning, it must be a native speaker. I imagine that when the effect of live human interaction is so profound compared to video, then books must really suck.
What does work for language learning is real-world interaction -- the summer is coming, so plan a camping vacation in your neighboring countries; that will provide lots of opportunity to play with other kids that speak a different language. Or find some kind of regular multinational community gathering in your neighborhood.
This language researcher provides evidence that watching video has limited learning effect and that effective learning requires live humans (as opposed to audio or video recordings): video presentation, article.
The BBC's CBeebies for pre-school kids currently runs a series called 'The Lingo Show', which aims to give kids an introduction to different languages. It's fairly well supported online.
There is also Same Smile which "explores the UK celebrating diversity of children's lives".
Last but not least, is our current household favourite, Rastamouse!
My son loves Pocoyo, and you can find the episodes on youtube in multiple languages.
Also, I don't know if you have BabyTv where you live, but "manny a la obra" is about a boy that fixes stuff with talking tools and alternates between talking in English and Spanish in every episode.