This is an online learning tool that is primarily focused on languages. It's free, and users can contribute where they have knowledge to give. It uses different ways to optimize ones ability to remember the content, as well as being structured in a fun way. In the language course I'm taking, you have a flower for each word you're learning about, and after you've been through it a few times, you 'plant it in your garden', and water it occasionally, by being given different tasks, i.e. writing it phonetically, or using it in a context, in order to solidify the content into your long term memory.
There's also other topics than language one can delve into, but I only discovered this yesterday, so I haven't had time to check it all out yet.
At the moment I'm learning Mandarin, and by now I know 25 signs, and how to pronounce them. Roughly anyway
Here's the website:
You have to register in order to save your content, but if you don't feel like it, it's not compulsory for using the site.
Feel free to move this topic somewhere else, if there is a more fitting location.