Duolingo is alright, but there is currently no Japanese lesson module (or almost any language that requires a non-Roman script). I picked up and trained some French using Duolingo, however it wasn't my favourite means of learning.
I used mainly whatever lesson videos I could find on Youtube. With the correct tools, you can download these videos and save them to your smartphone to listen to. Videos are much better than Duolingo for pronunciation, because real people are actually doing the pronunciation and not just a robot (which actually tends to mispronounce the words).
There is a Japanese section on about.com -
Free Japanese Lessons – Learn the Japanese Language - which would be a good resource. It's not necessarily a lesson programme, although there appears to be some sort of "free lessons guide" on it, here:
Start Learning - Free Japanese Lessons . I used the French about.com to help me understand some of the finer points of the language or specific things, e.g. how to express the past tense, or why two related words are used in certain situations, or how to say "I love you", etc.
If you are learning Japanese - or any language for that matter - practice getting the pronunciation right. This can be difficult without experiencing it in real life with another Japanese (particularly, native) speaker, but try your hardest. In particular, try to master the pronunciation of the Japanese "r", the difference between short and long "o", and "double consonants" (written with small "tsu", e.g.
yatta,
nippon,
dotchi...)
Gambatte kudasai!