I often record Japanese words that I experience, but do not know yet.
Kind of like what Tae Kim is doing here.
Lately, I have been making an app that allows people to do this without pen and paper, also it allows you to review new words more easily, across any site and many textbooks. Here it is!
One side effect of being able to keep your learned words digitally is you can compare resources, and see where you are learning most
Since, I also use Wanikani I wanted to add that in as a source. So I did that today.
Wanikani learned words can be pulled in via API. You can then compare your learning vs other sites or books that you use.