There are plenty of ukulele chord charts online for standard soprano tuning (gCEA re-entrant). You can find chord charts in both PDF, doc and jpg format on this page. But my favourite is this ukulele chord chart which gives you the fingerings for the chords in the fretboard dots and also arranges them according to how often you are likely to need them to play songs. Very useful for beginners.
For a more interactive and decorative chord chart (of sorts) check out Sheep Entertainment. But be careful with the tuning as the default is D tuning.
Ukulele Chord Books
The online chord charts are perfectly adequate for beginners. But if you want something entirely comprehensive, it’s worth investing in a ukulele chord book. At $5 and 1,000 chord shapes, the Hal Leonard Ukulele Chord Finder is well worth the investment for ukers looking to expand their chord vocabulary.