Delphi3D

Site focused on 3D graphic and especially on OpenGL. You can find articles, many samples in Delphi and links to some other interesting sites here.

NeHe

Many OpenGL tutorials, well-written and with source code. Source code is available in more programming languages.

Sulaco

Site about OpenGL with samples mostly in Delphi.

VTerrain

Virtual Terrain Project is dedicated to terrain rendering. You can find here everything what do you want to know about it.