I think I've mentioned it before in other threads, but I'll repeat it here.

I was fooling around with open tunings for an arrangement of Galveston Flood and hit one that I liked — an open C tuned, bass to treble — C G C G C C, with the E note achieved by bottlenecking to first string (treble E) at the fifth fret. It gives a really throaty bass without putting the trebles into the bat-cry range. Also found it works well for a version of Tom Rush's No Regrets.

Other than that, I mostly use open G, open D, drop D and standard tunings.

cheers

david