While I would like to think everything you need to know can be found in this website, I know that this is simply not the case. There are a lot of really good resources out there that can help you develop as a musician and as a pianist specifically even further. I’ve tried to limit the number of sites I mention so as not to inundate you with options. Here are 3 really good sites that I have found that can help you even further.
This is a blog that discusses a wide range of topics that relate to piano and music theory. While the name of the site suggests it focuses solely on learning piano chords, there are a lot of very informative articles on other related subjects. Having difficult memorizing your pieces? There’s a great article on this site for that. Want to know how to maintain proper posture when practicing? There’s an article for that as well. Want to know what the most basic chord progressions are on the piano? There’s an article for that as well. You will be able to find a lot of great information here that will help you become a much better pianist. Give the site a read-through and refer back to it whenever applicable.
This might be the most authoritative site on the piano solely because of its very active forum. You can ask any question related to the piano or music theory and you will get a really great response from an established teacher or pianist. It is a really great community full of teachers, students, and pianists that are all very helpful to each other. You don’t even need to really ask any questions, as you can simply read through the very large archive of forums threads and you can probably find the information you were looking for. This is a really great site.
If Piano Street is the most authoritative site on the piano on the Internet, then Piano World might be the second most authoritative. It differs from Piano Street in that it has a lot of information about pianos (how to buy, what to buy, etc.). It also has a really active forum of students, teachers, and professional pianists that can be really useful too. Definitely give this site a look if you are looking to improve your abilities. If you read through this site and the other two that I mentioned, you will be well on your way to getting better as a pianist (in addition to reading my site of course).