There's a Line - Polygon collision detection over at Sulaco.

I've converted the world collision tutorial at gametutorials.com to Delphi. It uses the VCL and there are some things that need to be fixed (mostly procedures that need to be changed from: procedure whatever(pVertices: array of TVector3f) to: procedure whatever(var pVertices: array of TVector3f)) and there's no comments . If you still want it you can give me your email so that I can send it to you.