See this article for information on one study.
To be reworked:
"When do People Learn Languages" is a fascinating article. I picked up on it because it was saying things I've been trying to tell people for ages: Kids don't magically learn languages; The FrozenBrainHypothesis? is almost certainly false. It's just that kids have all the time in the world to perform a terribly pressing need: To communicate with the people around them. But there's so much more in here! I highly recommend it.
One quote from the article: "Quite a few studies, in fact, find that adult learners progress faster than children".
I am surprised no one has created a web site with pictures, audio, or video of memory journey to use for the most common words in different languages. I have some old Easylearn tapes for Spanish from Learning Strategies (Paul Scheele) that use the concept of a memory journey in combination with mind maps in the booklet. The work is heavy on audi0 descriptions but very light on the visuals. It is easy to find a list of the most common words in any language. I would love to find a list of the most common words that includes a picture and their spanish (or german, french, etc...) equivalent.
Something like "The First 101 Words in Learning Any Language"?
I have just stated using the Link Word concept (by Dr. Michael Gruneberg) to pick up Spanish again. The LinkWord concept helps you learn commom words in a foreign language by linking the translation of the word to another english word, and prompting you to create a visual. For example, the spanish word for rice is ARROZ. The visual is several arrows flying into a plate of rice. I have gone through about 40 words so far, and had good success. But some of the connections are becoming more and more tenuous.
Barry F (5/25/07)
"Languages and cultures the fun way: Articles, essays, comments on learning languages" http://logoi.com/logoi_notes.html
_The Language Imperative: How Learning Languages Can Enrich Your Life_ book by Suzette Haden Elgin http://www.perseuspublishing.com/focus5.asp?ISBN1=0738204285
"Is English Learning Slowed Down with Bilingual Education?" seems to imply just the opposite. It implies that bilingual education gives students better English-language comprehension over the long term than English-only education.
"Anyone can speak 7 languages" "LEX Language Project is a multilingual education program where both children and adults can acquire several languages simultaneously." http://lexlrf.org/
Mudrast (30/04/2012) How I learned French in One Year 
Language-learning humor: ""LOL-Kitteh as a Second Language" :-).