Every once in a while, I've been reading the articles in this interesting blog[1] that covers various topics on procedural world generation. I've found that some of the articles (like, for example, this one[2] covering the creation of vegetation using space colonization instead of L-systems) are very educating.

[1] http://procworld.blogspot.com/

[2] http://procworld.blogspot.com/2011/02/space-colonization.htm...