Open Tunings

I'm starting to get into Leo Kottke and finger-style, and was just wondering if anyone could point me toward the basic open tunings.

Here are some. I personally like to use Open G.

Leo is awesome. I went to collage with his cousin (true story)

I don't know an resources tune to a D sometimes just to mess around

I'm just bringin' it up cause I'd really like to know more about them and which and when and how often and how excactly you guys use them...

I use Open G on my acoustic for playing slide guitar. Sometimes it's fun to just strum around on it too, but I don't really know the chord shapes for it yet.