There is a free iPhone app that helps finding a good list of cavaquinho chords

http://itunes.apple.com/kr/app/cavachords/id361656486?mt=8

Although not cavaquinho related,  it is good to know the theory of chords. I often use the following site:

http://www.harmony-central.com/Guitar/chord-and-theory-chart.txt

There is a nice list of cavaquinho chords online accessible here:

http://cavacoprodgbd.badiuforti.com/

This comes from an iphone application. It does not display some chords though (such as A#)

Sometimes ago I found a simple of all cavaquinho chords that could fit one page. I could not find it again but I did have a print so I did sum-up the content here

Soon chords and rythms to play on the Cavaquinho.

For now some existing links (some auto-translated in Brazilian-Portuguese):

• Mini-Course of Cavaquinho (original)
• Some rythms and resources