Ask HN: any hierarchical checklist software?

I need, for my day job, to be able to track the very same work breakdown for 5 to 10 different projects in parallel. The work breakdown is very structured, hierarchical.

But I cannot find a way to track to do items in a structured/hierarchical way.

Does anybody know a (good) hierarchical checklist software ?

------ Example of what I am looking for (it's really a simple thing, but I cannot find it):

[ ] is a checkbox Using the car work breakdown example here:http://www.expertprogrammanagement.com/2010/03/wbs-work-breakdown-structures-everything-you-need-to-know/

Make a car [ ] -- Make the engine [ ] ---- Make the cylinder [ ] ---- Make the cam shaft [ ] etc.