Free Navigation Program with AIS

Most people are familiar with Seaclear as a free navigation program with AIS to see ships. I just discovered, at least new to me, another and, I think, better one. For the link, just click on the title or goto http://opencpn.org/ocpn/
You can get free charts from NOAA, but you will need an AIS receiver and antenna to make that work. Otherwise it looks like a really good general navigation program. Certainly the GPS is quite accurate. And it is FREE! Don't want to bother downloading NOAA charts? There usually is a disc you can get cheaply on EBAY (about $10 +/-) with all the charts.