Pimsleur Japanese Language CDs
Pimsleur CDs, while expensive, are an excellent way to improve your basic conversation skills.
The Pimsleur approach is to listen and speak for thirty minutes a day, every day. The program is divided into three levels and there is one month of material per level. Different from nearly every other language program, these CDs actually help you speak. It's not just listening; the voices will prompt you to carry out conversations as you listen. (This makes it hard to listen to on the train, bus, and other public places because you really need to talk out loud to get the benefit.)
Like Mnemosyne, the Pimsleur CDs use spaced repetition, which means that even as you cover new material you are optimally reviewing older material, meaning that you will forget far less and remember much more than traditional language tapes. It also means that you shouldn't listen to several tracks per day, even if you have a few free hours; the CDs will work best if you can do 30 minutes a day, once per day.
The only really bad thing about these CDs is that they are very expensive- almost as much as a college course for the entire set. Although I think they're worth the money if you have it-- I used them to kick-start my study of Japanese many years ago-- many local libraries also have copies in stock, which is a great way to enjoy this excellent program without a huge outlay of cash.