See the original text and more comments here: http://www.sriraminhell.com/2008/10/make-your-home-smell-fresh-for-free.html
Step 1: What You Need
2. A few drops of any essential oil (substitute with Vanilla or any food grade essence if you're not yuppie enough to have essential oil around)
Step 2: How to Go About It
2. Work the spray action a few times to get rid of any fluid in the nozzle and to fill it with fresh tap water.
3. Take the nozzle out of the bottle and dry spray a few times to get rid of the tap water.
4. Pour a little tap water into the bottle until halfway.
5. Add 5 drops essential oil or Vanilla essence to the water in the bottle.
6. Shake thoroughly until the mixture forms an emulsion.
7. Spray in the room like you would with an air freshener.
Step 3: Misc. Notes
The Lemon Grass essential oil based room freshener's smell reminded me of a popular Indian pain balm called Amrutanjan. I also noted that the essential oil mixture wasn't that effective the following morning. So avoid storing the mixture for long periods of time.
Essential oils can usually irritate the skin when in direct contact, so take care when preparing the mixture. Also avoid getting the mixture in your eyes.
Just try this technique and experiment it with different essential oils and fragrances and let me know how it worked in the comments.