Has anyone used S3TC? It would be helpfull, if anyone had source to a program using them, or something else with the actual code.

It’s very easy. Look for the GL_EXT_texture_compression_s3tc extension. If it’s available you can replace GL_RGB8 (or whatever format you’re using) with GL_COMPRESSED_RGB_S3TC_DXT1_EXT and the driver will do the rest for you.

You looked at the doc that Nvidia wrote on their page?

Take a look at it, it’s quite good.

Further down, somewhere