Never one to do anything in any kind of order, I'm currently taking a look at Prestige Classes that will show up in the campaign. I'm into Complete Warrior at the moment, and I must admit, I've never really looked through this book thoroughly.
As I do now, I see that:
a) There are a boatload of Prestige Classes
b) There is now way I could allow all of them for PCs
But this does bring up an interesting point. There are some PrsCls that would make excellent opponents, but not so great character classes. So it's going to take some work there to lay out what is actually available.
In other developments, I've narrowed down the books for the campaign to be the PHB, DMG, and the various "Complete" books.
I've really got to tackle the cosmology next though. That was truly one of the parts of the first campaign that I knew what I wanted, but since it wasn't sketched out well enough, it didn't quite work as well as hoped.
I should try and set some internal schedule for developing this world though. It may be easier now than before, as this is likely to be my only gaming outlet for some time.