I use Drop-D, Double-drop-D, Open D, Open G, and DADGAD fairly regularly, so I'm comfortable with them. I find that going beyond that and trying to use too many different tunings inhibits me -- since I'm not that familiar with them, I don't intuitively know where to go next, which means that I can't really improvise, but have to stick pretty close to the stock arrangement. Since one of the real joys in my life is improvisation, I generall stay with these few tunings so I'll be comfortable working things out on the fly.

I have also heard DADGAD referred to as an alternate "standard" tuning, but I have to disagree. Five of the six open strings are either the root or fifth of a D scale (in every commonly used mode), so it clearly steers you towards some variant of the key of D. You can play in another key in DADGAD, but the tuning is not equally well suited to other keys in my opinion.