I am wanting to seriously brush up on my Spanish, but also want to learn several other languages - I had a language program suggested to me at one point, but can't remember for the life of me what it is. It's supposed to be better than the Rossetta Stone Language program. If you have used a program to help you learn another language, could you please let me know what you've used and how it's worked for you?
The serious answer to this question is that you cannot learn a living language to any decent degree without living in a community that speaks it and refusing to speak you own. Under those circumstances, grammars, pronunciation helps, etc. can make a huge difference in one's competence.
Baring that, watch dubbed and subtitled TV programs and movies (especially ones you already know well and enjoy) in the language you wish to learn.