When we talk to customers and get past the "who and why" part of the process of designing a site, we present spreads showing the layout and navigation.

The spreads are done by a designer in the tool of their choice and are usually a couple of pages showing the visual design. But we like to present a navigation proposal along with the spreads so the customer gets an idea of how the site will hang together and page relationships.

I am looking for an end-user friendly (preferably) online tool to quickly mock up site navigation. Ultimately, this is just a series of labelled boxes in a heirachy, with some interconnections. Some facility for defining where the connections come from a main nav bar or a footer menu or a side nav etc would be useful.

Currently, this would be done in something like visio, but this is overkill for something that happens and the non-technical end of the process. So I am looking for a tool that can be used to quickly mock up page relationships by someone non-technical.

I have been looking at the various wireframing tools out there, and some do provide what appears to be an easy way to get page relationships setup, but are still aimed at a designer/developer.

It occurs to me that perhaps it isn't a web design tool I am looking for at all, just a general purpose flow mapping tool?

Any suggestions?