VTFEdit
VTFEdit is a GUI front-end to the functions contained withing VTFLib, an LGPL open source programming library, created by Neil "Jed" Jedrzejewski and Ryan "Nemesis" Gregg.
VTFEdit itself was written soley by Ryan and is a .NET based GUI tool for the creation and convertion of VMT and VTF files. It is a powerful tool allowing files of various formats to be converted to/from VTF format in all of the Source texture formats.
VTFEdit produces MIP maps and DXTn compressed images of far greater quality than the default SDK tools and is highly recomended for those where visual fidelity is important.
Other features include the ability to create Normal Maps from grey scale images, various filters for MIP Map generation access to all VTF header flags and a simple tree based VMT creation system.