UkuChords brings you the ultimate ukulele chord referencing tool! Very advanced, extremely easy to use and above all completely free. Default tuning is GCEA (standard or C tuning) but you can simply select one of the quick tunings (soprano or baritone) to change it immediately. Advanced users can click on the notes in peg heads to even create your own tuning!
After you have selected your tuning you need to first select a root note (e.g. if you are looking for the Am chord, the root note is 'A'). The final step is to then select one of the many chord types available, all of the popular ones are included as well as some more exotic ones. Not happy with the fingering position on the fretboard? Use the arrows in the headstock to look for an alternative playing position, isn't that cool?
UkuChords also got you covered when you're offline! You can download a A2 poster or A4 PDF document which includes in total 180 chord diagrams for all keys. This is not only available for standard (C) tuning, but also for baritone tuning (links below)!