JapanesePod101 is a web site for learning Japanese. I have previously used ChinesePod.com for learning Chinese, and found it the most effective way to learn a language, so I was already familiar with, and enthusiastic about the format. However my Chinese level is beginner while my Japanese level is more advanced. My review is based on the 7-day free trial, and is from the point of view of someone with already strong Japanese skills.
Lessons are organized by levels, from Newbie to Upper Intermediate. These are shown as buttons along the top of the Lessons page. But the links on the right include some extras, so better to use them. Lessons are also organized by series, within the same level. So there is Lower Intermediate Series 1, 2 and 3. This distinction is confusing and unneccessary.
Each lesson has an audio lesson, generally about 7-12 minutes long, which has a dialogue by Japanese voice actors, and introduced by at least one native Japanese speaker and one native English speaker. Then there is a lesson notes PDF, which I found to be well-done, especially with the grammar discussions. In fact, unlike ChinesePod, there is probably good value in going for the Basic ($8/month) subscription. There is also a kanji PDF, but that was less useful: it is designed for tracing, but doesn't indicate stroke order. Better to buy a kanji learner's dictionary and use a piece of scrap paper.
Each lesson also a video showing the movie. I thought this was useful. My only criticism here is that it could be done as a flash movie, which would reduce the 10Mb file down to about 200Kb.
A few odds and ends. They have JLPT tests, but only for levels 3 and 4 (the easier two levels). There is a lesson called audio blog, which is all Japanese. The blog itself is only a few minutes long and is then followed with discussion (also in Japanese). They have special offers, both during the trial (wait for day 5 at least before signing up!), and every month or two after that.
The 7-day trial allows a maximum download of 10 PDFs (with lesson pdf and kanji pdf counting as one each), which caught me by surprise and effectively cut short my evaluation. I didn't notice any other restrictions however.
Summary: even for the more advanced student I think the lessons are useful, and I intend to sign up for a month's hard study in the Autumn. If and when they add tests for JLPT level 1 and 2, it will be even more useful.
P.S. I see ChinesePod.com are in the process of setting up JapanesePod.com. Given the headstart it has, I expect JapanesePod101.com to be superior for at least the next year.