Nested navigation approaches

I'm looking for a good way to have primary and secondary navigation. The idea is to have 2-3 big categories and 5-6 small categories for every big category.

I don't want to use nested navigation.

I'm tempted to use the following approach:

1 - Big categories using regular horizontal navigation (header)
2 - Dynamic vertical navigation for small categories(right or left)

What do you think about this approach? Do you recommend another approach?