http://www.tcd.ie/civileng/Staff/Brian.Caulfield/3A1/3A1%20Lecture%2013.pdf one of several on clothoid road curve generation . Good reference numbers.
http://hpcg.purdue.edu/?page=publication&id=170 (hydrography based terrain gen)
http://www.youtube.com/watch?v=GJWuVwZO98s (grid & layer system for infinite generation)
http://www.youtube.com/watch?v=RAtdFKiqs34#t=143 (procedural rule expansion based on voronoi of a plane created with distorted hex grid)
http://www.youtube.com/watch?v=FR9xI0GgrBY (by the guys who made Prison Architect!)
http://www.world-machine.com/download.php?page=basic is a pretty slick node-based procedural terrain generator. No scatter/foliage etc, but generates very nice heightmaps with neat erosion filters.
http://www.joesfer.com/?p=22 An interesting discussion of procedural weathering. The particle paint feature in Substance Painter has been really cool, this is in a similar vein
Not tried yet: