TinyCards.com (from DuoLingo.com) is a great tool for creating flashcards. You can save the individual chords from UkuleleGo.com and paste them into the flashcard maker.  Here is an example I created.

TinyCards.com - Ukulele Chords FlashCards

 

Ukulele Chord Cubes would be great to use like dice or something like that.  Here are some sold by Ukulele Magazine.

Ukulele Chord Cubes from UkuleleMagazine.com

Ukulele Chord Cubes from UkuleleMagazine.com