If you are new to programming or if you have the patience to work through a textbook:
How to Design Programs is the best place to start. Whenever the book says “Scheme,” you can read it as “Racket.”
Continue: Web Applications in Racket introduces you to modules and building web applications.
The Racket Guide describes the rest of the Racket language, which is much bigger than the learning-oriented languages of the textbook. Since you learned functional programming from the textbook, you’ll be able to skim chapters 1 and 2 of the Guide.
If you’re already a programmer and you’re in more of a hurry:
Quick: An Introduction to Racket with Pictures gives you a taste of Racket.
More: Systems Programming with Racket dives much deeper and much faster. If it’s too much, just skip to the Guide.
The Racket Guide starts with a tutorial on Racket basics, and then it describes the rest of the Racket language.
Of course, you should feel free to mix and match the above two tracks, since there is information in each that is not in the other.