Texture Coordinates

Texture coordinates, also called UVs, are pairs of numbers stored in the vertices of a mesh, and often used to stretch a 2D texture onto a 3D mesh.

UV Tutorials

How to plan good UVs is in the UV Theory thread on the Polycount forum.
Good methods for UVing spheres can be found in the Unwrapping a sphere thread on the Polycount forum. For sphere modeling tips see Sphere Topology.
A good weapon UV can be found in the tutorial First-Person Weapon UVs by Joe 'EarthQuake' Wilson
A good character UV example can be found in the tutorial Maya / Mudbox: Street Cop Workflow by Mashru Mishu.
How to prevent 3ds Max subdivision from distorting UVs is in the uv + turbosmooth= big problem thread on the Polycount forum. A similar thread: Best way to approach unwrapping UVWs with Meshsmooth?
For an automated UV projection system, see 3D UV projection network in Maya by Paul 'prolow' Lohman
What's an 8-sided tiled texture ? thread on the Polycount forum discusses how to edit textures so you can rotate and mirror them on adjacent polygons, without seams.
See also Light Map Texture Coordinates