VTFCmd is a GPL C command line frontend for VTFLib that can create VTF and VMT files from various source formats, and TGA files from VTF files. It is similar in functionality to Valve's VTEX Source SDK utility, but offers a lot more control.
VTFCmd supports Drag n' Drop or chaining files, folders and sub-folders using standard Windows wildcards. It can also resize source images, generate normal maps, perform gamma correction and more.
VTFCmd is part of the VTFLib library.