Can I subdivide page navigation?

I have a site with lots of pages, and the number of pages will steadily grow.

What I have at the moment is the following list of pages (dots added in this post for formatting)

* About us
* Client List
….o Construction
* Contact Us
* How to Find Us
* Services
….o Golf Course Construction
….o Sand and Gravel Banding
….o Sand and Gravel Bedding
….o Sand Slitting
….o Sports Field Drainage
….o Sports Pitch Construction
….o Sports Pitch Renovation

What I was after, if possible, was a way to add in a way of chopping up the way the pages are listed, so instead of the big list above, I could have two lists:

General:
========

* About us
* Contact Us
* How to Find Us

Services & Clients:
===================

* Client List
….o Construction
* Services
….o Golf Course Construction
….o Sand and Gravel Banding
….o Sand and Gravel Bedding
….o Sand Slitting
….o Sports Field Drainage
….o Sports Pitch Construction
….o Sports Pitch Renovation

This would then separate out the pages a bit, and keep things tidy.

I’m not sure if this can be done – just checking if anyone knows.

The site is here for your information:

http://cgi.nelsonriggott.plus.com/souters/

Thank you

Jim