This plugin is available at no cost via Mediafire. I did not tested it yet, the first impression after watching the video demo by VST Planet is that Ukulele is a basic instrument plugin with ADSR, Tune and Fine Tune, Velocity Sensitivity and Output Volume, Speed and Level controls for Vibrato and a 7-band EQ. The overall sound is not that natural, but with some processing, it will get more realistic.
Processed thru Chorus, Flanger and a subtle Reverb, Ukulele VSTi by Samsara Cycle Audio will offer a lot of fun.
More info: Ukulele free VST instrument