Hi,
On most project I use multiple layout scripts.
Sometimes I need some data in my layouts that are layout-specific, instead of page-specific. Which layout gets used though, IS page-specific.
So the bootstrap or actioncontroller would be good places to select a layout. But IMHO they would not be good places to inject the data a particular layout expects.
The only other place I can think of is to just write some business logic in the layout viewscript itself. Though that's something I'd rather not do either :)
Where do you write your layout-specific business logic?
-- UPDATE:
layout-specific business logic could be;
- username of currently logged-in user
- amount of new messages in user's inbox
- random "did you know..?" tip