Environment sculpting is the process of creating a high-resolution 3D model with a series of painting strokes, using 3D sculpting software. Usually the details from these models are baked into a NormalMap for a lower-resolution in-game model.
Sculpting Tiled Maps
Tiled Bricks and Stones
Creating Tiled Textures and Displacement in Mudbox 2009 - by Wayne Robson
Painting in Mudbox on the middle of a 3x3 grid where each quad has the same overlapped UVs. (video is about halfway down the page)
Pixologic - ZBrush - ZClassroom Digital Sculpting - Environments With Tate Mosesian
Video tutorial from Pixologic about using Zbrush to create tiled textures, by the Lead Environment Artist at Naughty Dog.
Pixologic Release - Learning Series: Tileable Textures
Video tutorial from Pixologic about using Zbrush to create tiled textures. Includes a free ZScript called Layer Shift that will enable you to shift all layers on your canvas half the width or height of your canvas (similar to the Offset Photoshop filter).
Tiled Cliffs and Grounds
Solutions for sculpting tileable textures (other than bricks) in zbrush 4 - Zbrush method to tile using an imported mesh and brushes with WrapMode.
Creating Perfectly Tiling Meshes in Zbrush for use in Videogame Environments - by Owen 'SHEPEIRO' Shepherd
Using ZBrush's 2.5D canvas to tile stamped meshes, then using Maya to model tilable geometry.
Sculpting Individual Objects
Sculpting techniques for creating individual non-tiling meshes.
Bricks and Tiles
Thread on Polycount about modeling weld seams.
Rock and Stone
Rawk - Post any rocks you make here! Polycount Forum thread
Quickly Making Large Scale Rubble - by Timothee Yeramian
Using 3ds max procedurals to quickly sculpt a concrete chunks.
Rough Wood Planks Tutorial - by Philip 'Philipk' Klevestav
Sculpting and painting a rough wood texture using Zbrush, 3ds Max and Photoshop. More sculpting tutorials at http://www.philipk.net/tutorials/materials/materials.html.