Easiest and one (but not the only one) of the best is Autoroute, even if it is a Microsoft product.
There are other cheaper and more expensive alternatives and all have their +'s and -'s.
Expensive way - TTQV plus Navtech maps - but very versatile and great with a GPS.
Cheap way - free cover disc of Route Finder or similar.
I have a few free ones on magazine cover discs. If one of those would do let me have your address and I'll send them.