Cheese sauce recipe?
Here's the sauce that goes in my mac-and-cheese, which I think would work very well: Heat 1 1/4 cups whole milk just to the boil. Add 8 oz. cubed cream cheese and stir until melted. Add 8 oz. shredded sharp cheddar and stir until melted. This sauce is very creamy and smooth and would take well to dressing up (other cheeses, green chile, etc). Incidentally, if you want the mac-and-cheese, this will sauce 8 oz. macaroni decadently.
The CI recipe is indeed good, esp. for mac & cheese :) When I make it, it tends to be a little bit thin, though (perfect if it will be baked, but maybe a bit thin for nachos?) I think the starch from the pasta is what ends up making it thicken up right-- maybe worth still adding a little starch or flour if it's supposed to stand on its own?
In a rather different vein, you might also consider a "beer cheddar fondue" recipe, which has a mix of beer and cream for its liquid
I recommend combining some velveeta with some other cheeses (monterrey jack, cheddar, etc) and using spices (garlic), along with some Rotel or homemade equivalent. When I make queso, it usually has:
sweet (1015) onion
fresh serranos (or jalepenos)
fresh red bell peppers
if you combine them all, you'll lose the velveeta taste, but keep the creamy quality.