I have been using Open CPN as chart viewer and route planning software. It seems to be quite powerful for a free program. You can learn more about it here. http://bigdumboat.com/cpnfaq.html

I used openCPN all last summer on my boat as my only charts. The features are great, it uses official NOAA charts and being open source is a big plus for me too. Since I pulled the boat out in October I know they added support for making tracks and other cool features like a mooring alarm.

Update:
OpenCPN is back in action out on lake michigan running on ubuntu linux with a 23" flatscreen monitor, big enough to read from the cockpit of my little sloop, I find it more then adequate for my needs and if anyone wants to check it out let me know.