Do you guys recommend any workflows for generating terrain in Blender? Do you guys use a plane and the displacement modifier, with voronoi and cloud textures? Or is there something more evolved, with erosion, etc? Do you recommend any good book or video website? Thanks! 
i make things for a 3d space sim
so. What kind of terrain ?
a square area
part of a map ?
a WHOLE planet ?
a asteroid ( real one or not )
something like this "work in progress " that i put on hold
( derived from the black and red maps in the hard cover books )
middle earth was done using “wilbur” and Gmic ( from the bash terminal )
imported using “import plane " ( rgb texture) then a displacement modifier " the height map”)
or a full planet - very early still and needs a lot of work " Kepler 452 B" – in the news from NASA lately
For the above planet . Blender was used ( ant - spherical ) to make the base mesh and burned to a Displacement
then eroded using wilbur the full size of the “dem” above is 5760x2880 32bit float
or asteroids
REAL ones like
Near Earth Asteroid Bennu / 101955bennu / 1999 RQ36
( there is a low resolution shape REAL DATA file - 1348 vertices )
that i augmented
each kind of Terrain uses different tools and different workflow
Oh, nothing complex, without using DEM data or anything. Just procedural terrain, like what these apps do:
http://codeflow.org/entries/2011/nov/10/webgl-gpu-landscaping-and-erosion/
http://http.developer.nvidia.com/GPUGems3/gpugems3_ch01.html
http://www.world-machine.com/
for basic terrain only you can start with ANT
http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Add_Mesh/ANT_Landscape
then fallow any of the node guides for coloring
for videos
a castle , but using ant
and lastly the wikibook “Blender_3D:_Noob_to_Pro” ( a bit older )
https://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/How_to_Do_Procedural_Landscape_Modeling