Exploring ukulele goes FAR beyond this course, and there are many free resources you can use to both polish and advance your skills. Here are a few of my favorites! (I will update as I discover more!)
I know, I know, it's called ultimate GUITAR, but there is an option to switch to ukulele chords or tabs within this resource! This online catalog has thousands of tunes, so search your favorites!
Similar to Ultimate Guitar but more uke friendly, Ukutabs is a searchable music database to find uke friendly songs and tips!
Youtube is full of fabulous resources, but this is a very user-friendly favorite. The Ukualiens channel has a number of tutorials and play-along videos, categorized by difficulty. Although some may seem simple, these play alongs also provide great practice for different strumming patterns and techniques!
If you are wanting to purchase additional resources...
You can always check out your local music store and see what they have to offer! They usually have sheet music, accessories, supplies, and someone willing to help out or demonstrate!