Try Seaclear. It's freeware, reads the free NOAA raster charts no problem and when connected to the GPS
, it automatically reads the boat location and selects the proper chart when it comes up. The software isn't intuitive, but after stumbling around for a while I can now easily plot a course and upload all necessary waypoints to the GPS.
I love the price (free), and it seems to have all the bells and whistles, meaning inputs for depth sounder, wind speed, speed log and on a 15" laptop wide screen it's easy to see the menus and watch your boat progress.
SeaClear GPS Navigation Software
I've been using it for over a year and it's flawless so far. The only limiting factor is being limited to available NOAA charts. It does have a chart import feature, but I have to admit that I've never used it.
Over all, it's cheap, and it works great. What else does a guy need? As far as USB GPS's? I picked up a Belk serail to UPS adapter. Load the driver and connect the GPS. Seaclear sees it just fine.