Standard, Drop D, Double Drop D. The Double Drop D is usually only on acoustic for Black Mountain Side/Song for George type stuff. And open-E on my lapsteel.
This for me too but I am primarily in drop C. Sometimes I will tune it up to D standard and every now and then I use Drop Bb which is pretty awesome sounding.
I don't use 7's anymore but when I did it was either Drop A or Drop G.
Depends on the band. Of the projects in recent years, my tunings in have been E/Drop D, Eb/Drop Db, and a couple of tracks only that were tuned in "Dropped Bb" (aka, the entire guitar is tuned down a half step except the low E, which is tuned to Bb). So, all of my guitars are tuned to either standard or half step down, then I retune the low E as necessary.
Bought the thickest strings I've ever had this weekend. Dr DDT-13's and have it tuned to drop A on a 6 string. There a little stiff but man it sounds awesome. Gonna stick it out and see if I can get used to them. If not I gotta go back up to 12' or 11's.