Red Blob Games has a ton of articles about game development, including several excellent ones on procedural generation. This one is a look at using polygons rather than tiles to generate a map. It uses Voronoi cells and Lloyd’s algorithm to generate the basic structure and then uses that to further refine the smaller-scale details.

What’s particularly helpful here is the breakdown of the reasoning behind the different sub-generators and how they fit together to create a cohesive map.

http://www-cs-students.stanford.edu/~amitp/game-programming/polygon-map-generation/