We use the Michel Thomas cd's. I know some people disapprove but after trying various other means, it's the only thing my DS's will do regularly & as there is no memorising or writing, they love it. V. expensive though & we bought off ebay - though beware of all the different versions.
Recently I did a free 24 hour trial of rosetta stone for French & it was really good but I couldnt say how that would be on a more advance level though they do say money back guarantee for 6 months.
It's funny that no matter how much studying or courses I do, I find French very difficult to retain but Latin & German are a swizz. Must be the wiring of the brain - they are far more logical to me & would suit a more mathematical mind IMO.
I had a conversation with my OH the other night about Midget not being any good at French and doesn't have an interest. We were going to see if it's all language's once at senior or whether he will pick up other one's such as German and be good at it, if not then we will have to do some extra work
Your comment on the mathematical mind I find very interesting and hoping my son is like this and will atleast be good at a different language