I am not an expert on any of these topics, but I thought it might be useful to compile resources by subject so that you wouldn't have to search the blog if you were only looking for one area of maths.
Let me know if there are any more you would like to see.
P.S. Don't be put off by the 'Introduction to...". People write pHDs on these subjects and won't even scratch the surface of understanding. Resources aimed at introducing topics often include helpful references to new notation and language.