I like QASANA for 3 separate reasons:

1. The style of learning. I find that whatever memory experts may tell you, some rote-learning of vocabulary is sometimes required, and has done me pretty well over the years. QASANA puts vocab in chunks of 20 words, all categorically similar, and then tests you on all of them, from your native language to the foreign language.
2. The breadth of vocabulary. 1500 useful words is a great start to building your active vocabulary in any language. (An active vocabulary being the words you could put into a sentence you construct yourself, whereas passive vocabulary are the words that you could recognize, but not necessarily recall for your own use.)
3. The site design. I really dislike using websites that are overly busy, have bad navigation, or are full of distractions, be it advertising, or just bad design. QASANA is so standalone and application-like, that I actually created an application shortcut (Chrome users know what I’m on about) so that I can just call the website up by itself, and use it distraction free.

Stumbler’s or avid internet users may have already come across  this website before but for those that have not, or needed reminding of its existence, I thought the resource had earnt its own post.