Start by dicing up 6 oz sharp cheddar cheese, 8 oz medium cheddar, and 4 oz monterey jack. Melt 6 tbsp butter over low heat (real butter -- no margarine). Slowly add 6 tbsp flour, stiring frequently. Once that's going zap 1 cup 2% or whole milk in the microwave for 45 seconds, then add it to the butter/flour mixture. Repeat this two more times for a total of 3 cups milk, then bring the heat up to medium-low.
While that's going put on a pot of hot water and start boiling 1 lb of elbow noodles.
When the milk/butter/flour mix is up to temperature, add about 1 tsp salt, 1-2 tsp black pepper and 1-2 tsp cayenne pepper, then start slowly adding the cheese. Start with about 4 oz of medium cheddar and 2 oz of the other cheeses, and then add more of each type of cheese as your taste necessitates. Depending upon the strength and flavor of the cheeses you're buying you may need to adjust the ratios, but I found that 6/8/4 sharp/medium/jack works for me. I haven't tried it yet but I think a hint of smoked gouda might serve well too.
Once the cheese sauce is ready drain the noodles and pour the cheese in. Mix it all up and bake for 30 minutes at 350.