http://www.omniglot.com/
This website has some good information about learning different languages. I read an article where children don't learn better than adults, they learn the language(s) spoken by their peers. They have more motivation in learning a language because they don't want to be the kid who speaks "funny." As an adult we don't have the time or motivation in which to learn a language, unless you're like me and live in a foreign country, and we don't give a damn about our peers ridiculing us. We think they're an ass and move on.
It has some good links to other pages for more info on learning another language. The site is worth a read.