This is one of the most comprehensive workflow Tutorials for Landscapes in blender.  He talks about how to blend textures, use meshes instead of displacement, and using lattice for randomness.   If you watch this video 3 times, first take the info in.  Second, take notes, third, Try different parts using his Add on. (free version)

For those of you who don't know Humble Bundle sometimes has tons of assets bundled for about 30$   They also have a awesome 1$ deals too.  

Grab, sometimes hundreds of Models, Set Pieces, or Characters for $25 or $30.

www.HumbleBundle.com

The secrets of luminaria contest.

3d total has quite a large free section of magazines and information relating to 3d.

You can get the free stuff here.