I've been watching this project for a while, and thought that you guys might be interested in seeing it. Please note that this is all still a beta.
Official Trailer With Info
This is the beta of Custom Mapping Team's Single Player Version 3 (CMT SP v3). It is a free mod of Halo 1 for the PC. I think it's amazing what they've been able to do with a 10 year old engine.