Man, you're going to have a great trip. If you haven't, be sure to check out the Surly Roadtrip Gems thread and map, there's a lot of good shit there which has served me well.
There's so much good stuff you can't do it all, but the upside of that is that you can't go wrong with any of the above advice. I especially concur on the Colorado route along the Arkansas river. Beautiful country, cool towns, and great people. Amigo Motor Lodge was a fun place to stay in Salida if it happens to fall that way on your route, and a good excuse to hit up some of the breweries.
I can't ever argue against going through Santa Fe, but if you want something more off the beaten path, I have a sentimental soft spot from my youth for the route going Ft. Sumner -> Santa Rosa -> Las Vegas -> Mora -> Taos. Blue Hole is a cool (well, cold) diversion in Santa Rosa, and you can drive through downtown Las Vegas and relive killing commies in Red Dawn. My family loves staying at the Taos Inn, and sitting in the courtyard there with a jalapeno margarita as the sun sets and the neon lighted sign comes on is one of those places for me which makes everything in the world seem right.
Hope you have a great time. Damn, I'm jealous. Not enough time off this summer for an epic road trip.