Recently, I completed an excellent Coursera Course: An Introduction to Functional
Analysis, offered by École Centrale Paris.
Although challenging, it was a fun and interesting course, thanks to the effort by Professors John Cagnol and Anna Rozanova-Pierrat. Functional Analysis is a pretty difficult topic, and it was great to have two good professors explain it.
This course is actually more suitable for students who have some mathematical background, especially in mathematical analysis. New students may find it too hard to follow it from scratch. It is excellent as a review course for students who have taken functional analysis a few years ago but have forgotten some of it.
Introductory Functional Analysis with Applications