[3.5] When you visit the Astral Plane...

[the Jester]

Of course, you can still only cast one quickened spell a round...

...without the Multispell Epic feat.

 

[Pants]

The Plane of Fairy is even better. All Arcane spells are Maximized, Empowered, and Extended. Super fun...

 

[Orias]

I prefer the town of Curst while I am playing Necromancers. A great increase in the power of necromancy spells & a negative for the saves against them.