Annie's mac and cheese (made with yogurt so it's tangy!)
I'd never thought of doing that, but it makes sense. I tried it the other day, and it really does make the mac tangy — thanks, GFJC! (Plus, eHow.com lists it as a way to make boxed mac and cheese if you don't have milk or butter.)
Which leads me to this ... There are probably a lot of these tips out there rattling 'round in our heads. Let's get them out in the open, where they're useful. What kitchen tip(s) do you have worth passing on?