These are the current seasons that have been released in the US. I broke down each of the actual seasons into what they are called on the DVD releases.

Season Guide:
1st Season: Indigo Plateau

2nd Season: Orange Island Adventures

3rd Season: Johto League

4th Season: Johto League Champions

5th Season: Master Quest

6th Season: Pokemon Advanced (Hoenn League)

7th Season: Pokemon Advanced Challenge

Spin Off: Chronicles