How can I break up the pages navigation (Plugin? hack?)

I would like to be able to break up the navigation of my site into different places in the design. I haven’t seen any way to do that yet though.

Here is what I want to be able to do:

In one nav block, list all root pages.

In a second block, list all the sub-pages of the root page the user is currently on, expanding and collapsing levels as the user delves deeper.

I have tried a ton of plugins, and can’t seem to figure out calls from the codex to get this to happen myself.

Thanks so much for anything you guys can come up with.