When effort is put into creating language training, typically the training is for people from one language to learn another language. This means that training material needs translating for all the other languages. This requires a lot of effort and, it would be nice if we can economise this effort.
At this time I am helping to set up training for Farsi. There are some issues with learning Farsi. The first one is that you need to learn the characters used in Farsi and learn to read from right to left. The second one is to learn the sounds that go with the characters.
Once you can recognise the characters and have learned a basic set of words, methods like "language immersion" can be used to learn a language.
Using wiktionary in combination with language training
When learning words/phrases, you have the word in the target language and, you need to know how it is pronounced. The pronuncutiation is recorded and saved in Commons. The words phrases are also defined in wiktionary. This way we can have as many translations for the Farsi word/phrase as possible defined in wiktionary
In the Ultimate wiktionary, words and phrases have a "Meaning" these will have translations in many languages and by combining it with the language of the user interface in use, the word or phrase in the "known language" can be projected.
A discussed extra feature around Ultimate wiktionary development is a mode for interactive language exercises. See ultimate_wiktionary_and_language_exercises
When we have useful phrases for topical situations, we can have photos with the pronunciation and text in the "target language". Individual words can refer to wiktionary.
By going for a phrase book and combining them with language training, we achieve two ends: they can be available as lists in wiktionary and they can be available in Wikibooks for learning a language.
How about a site that allows you to enter a URL, reads the page from that URL and turns every word into a popup with a short definition of that word? Example: I learn spanish so I enter the URL of a spanish newspaper and get that page verbatim except that each word shows a popup with an english translation when the mouse hovers over it. Presumable I'll know those words after using the mouse a few times.