I know you specified that you want a freeware app, but I don't have much experience with those. The freeware cartography apps I've seen haven't been all that impressive, creating only the most basic of maps or being incredibly complex to use.
What I use these days is Campaign Cartographer 3. It's really come a long way since its first two versions, and you can easily make maps that can rival those found in commercial RPG books. Here's
the map I made for a D&D campaign I'm currently running, for example.
The problem with Campaign Cartographer is that it's somewhat expensive, so it's probably not what you're looking for. If you're concerned about the quality of the finished work though, you should give it a look.