About eight months ago I began learning how to play slide guitar.  
And if have noticed there isn't a whole lot on the internet on the subject.  
I guess all of us slide guitars players will just have to figure it out for 
ourselves.  In this lesson I will tell teach you some alternate tunings 
for your guitar.  All tunings start with the low string to the high string.

Open E
E B E G# B E

Open G (most common)
G B D G B D

Open A (also very common)
A C# E A C# E

C6/A7
C# E G A C E

Now theres many many many more tunings than just these but this will get you started.

fifty