I used this free plotter software -
http://opencpn.org/ocpn/ on a laptop , with this GPS receiver
http://www.amazon.com/GlobalSat-BU-3.../dp/B000PKX2KA . I find laptop touchpads difficult to use on land, and almost impossible on a rolling boat, so grabbed a cheap trackball mouse for menu navigation. It worked great.
I ended up installing a DC->AC inverter and mounting a mini-ITX computer (with solid state drive) on the cuddy bulkhead, and connected it to a touchscreen. Works great, plus I have the added advantage of full internet access on my boat since there's open wireless networks everywhere.