Network Documentation

I am a network consultant for a large cisco partner and I am always looking for better ways to document my various clients network. I use Visio extensively for customer facing documents and proposals, but use Network Notepad to create diagrams for engineering use. I create a file with each clients name and merely insert all their diagrams and documentation into the one folder. I have been using this method for over 5 years, but somehow it seems crude. I am looking for any suggestions that have been tried and tested from others in the same field.

I am forced to run Windows XP Pro but run other various distributions in VMware if that is any help.

Thanks, and I look forward to your suggestions.