Insert Piz Here has released version 1.2.1 of the midiChords VST plug-in.
This update adds a configurable fretted stringed instrument view for chord input, basic strumming capabilities, and support for Mac OS X.
Currently donationware, midiChords displays a small "demo" text on the GUI when unregistered but there are no other limitations. Users can register by making a donation of any amount.
Source code is available under the GPL.