Language learners have been using personal notebooks for almost as long as the science of language study exists. When you encounter a new word, you write it down in your notebook. When you revisit this page, you recall the word and after a while the brain memorizes it. This approach certainly works and if it didn't, we wouldn't have polyglots who succeeded in learning languages in the pre-computer era. However, I'm sure that right now we can do better, in fact, much better. Using the power of computers we can store words and collocations, access our collections from anywhere, assign pictures and add contextual example sentences.
What's more, we can turn the revision into a semi-automatic routine. If you add several words every day, achieving proficiency level vocabulary is no longer a daunting task but rather a matter of time. The only remaining challenge is to make word entries as useful as possible therefore accelerating the process of memorization.
The service on this website, now available in beta, offers all of the above mentioned points and even more. It allows to add words and collocations, learn and revise them by doing automatically generated exercises.
In my experience, for simple words that have direct matches in your mother tongue, a single translation will suffice. However, as you progress, there will be many words that can be translated in your languages in several different ways. In this case, monolingual descriptions become really very useful. Lexical features are shown by tags such as 'uncountable' or 'formal'.
What is next
I encourage everyone to sign up and try using the service on a regular basis. The registration will be opened until the first 100 users are registered. After that it may be suspended for some time and then resume again. Keep in mind that it's still a work in progress, so breakdowns are rare but not impossible. On the other hand, I've been using it privately for quite some time and it's worked for me so far. If you find a mistake or simply want to provide some feedback, send an email to overfluent AT gmail DOT com.