Scent #1: Oranges, cinnamon & cloves (allspice and anise are optional). This is my favorite, both for its wonderful aroma and for its staying power. This scent carries into multiple rooms better, and it can be reheated to scent your rooms for several days.
Scent #2: Lemon, rosemary, & vanilla. A similar scented water is often simmering in Williams-Sonoma stores. It has a lovely freshness to it.
Scent #3: Lime, thyme, mint & vanilla extract. This combination has such a fresh, pleasant scent. I initially made it without the mint extract, but have found that it really kicks up the aroma.
Scent #4: Orange, ginger (fresh or powdered), and almond extract. This is a sweet, delicious scent.
Scent # 5: Pine or cedar twigs (or other fragrant twigs), bay leaves, and nutmeg. These scents combine for a complex aroma. If you have whole nutmeg, use a Microplane to grate off the outer surface--this will release the scent. Add the whole nutmeg piece along with the gratings.
Here's the gang of five. Aren't they beautiful? I like to make these up in pint jars and keep them on hand in the fridge so I'm ready to start a pot of simmering scents as needed.