So MongoDB University is another great website for many many tutorials to learn MongoDB in depths, of course for free.
The full course catalog includes courses in general on MongoDB but targeting specific languages and frameworks. This website is a very practical one, especially if you started to think about building databases and collecting data. Another great thing about these courses is that you can actually receive a certificate for the completed lessons.
Recently I came across this very useful site (Web Design in 4 minutes) via a friend of mine (@thedevgirl).
Basically think of this as a game, you keep clicking as it would be an adventure game and you keep going to explore and more details about the beauty of web design. It helped me greatly to put my CSS knowledge into place and revise what is what.
Also the site shares very important details and principles how to build a project or portfolio, so keep on reading and have fun clicking!