There are so many great Excel resources on the web that cover an absolutely massive amount of topics.
To begin with, in the interest of keeping this list short, I have narrowed this down to the 10 resources that I have found the most helpful and comprehensive, from the official Microsoft Blog, to a range of personal blogs covering many different aspects of Excel.
This list will likely expand over time, and if there are any that you feel should be added please feel free to reach out (either via email or Twitter, preferably Twitter) and I will look into adding a link.
The current list is as follows: