I enjoy learning Japanese. After giving up on trying to be ready for the JLPT this year, I found this website. Let me tell you, it is awesome. It is a simple program to use yet you cover many levels of the Japanese language in an easy to understand format. Also, through this site, you can become friends with Japanese who are on the Japanese version of this site. They use iKnow to learn English and through messages, photos, and journals you can communicate and share language tips.
The website is totally free and is continuing to morph into something wonderful. Users can create their own vocabulary lists and share them with others. Maybe you want to learn some of the Osaka dialect. There is a list just for that. Perhaps you need help with listening skills. This site has you covered. There are other features at iKnow available for Japanese language learners...and the pictures used are of excellent quality. Also, if you have feedback the admins are there to listen and will reply back promptly.
Don't worry about Japanese input or Japanese font to use the learning part of the site. If you want to type in Japanese in the journals or forum you will need your own input program however.
Give it a shot and report back here to your findings. I haven't found anything better (that is free) just yet.
Note: This site uses flash. Other than that no downloading required to use this excellent website.