Ukulele Underground Forum
https://forum.ukuleleunderground.com/
Extensive and friendly discussion forum.

UkuTabs
https://ukutabs.com/
Collection of chord charts and tablature for many songs.

Ukulele Chords
https://ukulele-chords.com/
Searchable database of chord diagrams. Provides diagrams, fingering, numerical
notation, photos of fretting hand (for many, but not all chords), alternative
positions, etc.

UkeBuddy Chord Namer
https://ukebuddy.com/chord-namer
Lets you select notes on the fretboard and it tells you the name of the chord
they form. There are also other tools on the same site.

Got a Ukulele
https://www.gotaukulele.com/
Ukulele reviews and beginner tips.

Ukulele Underground Beginner Chord Chart [PDF]
https://ukuleleunderground.com/wp-content/uploads/2012/09/ukulelechordchart.pdf
The clearest printable chord chart I've found so far.