Seems 3D Realms got scared and pulled the links.

Second and third links still work.. Anyway the Ultra quality is good, but kinda pointless. Requires a video card with at least 512mb of memory. Uses uncompressed textures, Ill stick with high quality, nice compressed textures :)

Do you even see the difference in compressed and uncompressed textures without a magnifying glass? At least the games I played never showed a real noticeable difference with uncompressed vs compressed textures.