Also there is a superb online free chord library offering the largest and the most comprehensive selection of ukulele charts from uke planet. The archive includes a complete list of slashed chords and an extensive collection of photos and sound samples together with plenty of additional information about the chords, such as intervals, alternative positions, fingerings, difficulty, usefulness, similar chords/fingerings, and much more. Check it out.
For those just starting out with the ukulele as well as for those a little down the road already, there is a superb video training course from ezfolk.com The course is designed especially for beginners but should also be helpful for anyone who needs to expand their basic knowledge of playing ukulele. All of the lessons are free and include 19 songs covering 5 common keys (C, F, G, A, and D) and more than 20 different basic chords. These lessons will provide a foundation for subsequent lessons featuring more advanced techniques.