For HeroQuest, the best mapper is
HeroScribe. Phoenix introduced me to it and poked me repeatedly with a sharp stick until I started trying it out myself. It's fantastic. Has both European and North American style, and icons for all the official expansions. I hope that Derfel Link can finish and release the long awaited update. It would be great to be able to design unnatural maps with it. Even better if it had an import icon feature. Then when new tiles are released we can easily mark them on the maps.
There are a few fan created PC games out there. Ye Olde Inn has links to these on the PC game page. I don't have any of the official PC games to put up.
Feel free to start a thread with a collection of link's to HeroQuest programs and mappers.