I think that Clinton Hammond used to have a link to DADGAD chords on his site.

If not I have a pdf I could send you.

I went to a guitar workshop at Hardraw with Duncan McFarlane (if I have the name wrong my apologies) who sent us a pdf of C modal tuning chords which I'll forward if he doesn't mind.

The Dougie McLean website has links to the tab site associated with it which has lots of practical stuff about open C in the context of Dougie's songs.

The Joni Mitchell tabs site here has so many tunings and ideas you could lose yourself for ages.

Or you could work them out and find new ones!

What is this chord - Open C tuning (CGCGCE) - 205050 - it's a current favourite of mine? (DGFGFE are the notes - Dm11 perhaps? - fingerpicked it's nice with the FE playing against each other). It works in that tuning but not in standard tuning or most others. It's the options that tunings open up to sound different rather than the ability to play standard chords that is the point of them isn't it - or I may have missed the point as usual?