I've been enjoying lurking on here for a while, and this thread finally incited me to join the forum!
I'm a pretty new dobro player coming from the woodwind world and have been (probably foolishly but stubbornly) playing a one-octave harp tuning that I came up with after much experimentation. It's the same notes as the tuning b0b just posted, but stacked in close spacing. Low to high:
D F# G A B D
It's rough having the reduced range and hitting the wrong string nearly always sounds bad, but it has some pretty neat characteristics:
Nearly all the triad inversions from C6 (can't do minor with the fifth on top) for chord-melody.
Sus or add 4th with resolution to the third in the same octave.
m7 and M7 with no open strings (though it's really a second with the close spacing).
Some cool slant/pull things:
Forward slant on strings 1,3,5 across 2 frets, pulling the top string in tune, gives a dom7.
Forward slant on strings 2,5,6 across 1 fret, pushing the bottom string away from you to fix the intonation gives another dom7.
Forward slant on strings 3,5,6 across 1 fret, pushing the bottom string gives augmented.
If you use a bullet on the back end of the bar, a back slant on strings 1,5,6 over 1 fret gives a M7.
I think it would be a lot more fun as an 8 string tuning, adding the low G and B strings from standard dobro G to the bottom of it. This would give minor with the fifth on top and better voicings for seventh chords.
It's very versatile for jazz and pop stuff but probably cripples me for normal bluegrass stuff. I've been told I should just start learning pedal steel instead, but I love the sound of dobro too so I'm torn.