As you know, I've been making my own 
laundry detergent now for a couple of years, and love it.  For those same couple of years, I've been trying to find a dishwashing detergent recipe that I liked.  I've tried probably a dozen different combinations and recipes over time, unsuccessfully, but I've finally found one that I think actually cleans as well or better than the expensive store-bought stuff.  The KEY is using Lemishine.  Lemishine is a product found next to the rinse aids in the dish soap aisle.  I buy it at King Soopers (Smith's) or Wal-Mart, and have noticed it at other grocery stores.  The other ingredients are things I usually have around my house, because many of them double as the ingredients in my laundry detergent recipe.  I have been washing my dishes with this for about 4 months now, and am really pleased with the results.  I had a friend move and she gave me some liquid dishwashing detergent, so I have been using that for the past couple of weeks instead, and it doesn't come close to comparing to the quality of this homemade stuff!  I finally threw the last little bit out and just switched back to this homemade stuff because it's SO much better.
Ingredients:
- 1 cup Borax
 
- 1 cup Arm & Hammer super washing soda
 
- ½ cup kosher salt
 
- 1 cup Lemishine 
 
Mix everything together and store in a plastic container.  Use 
1 Tbsp per load. 
 I put this in the dishsoap section that doesn't have a lid covering it.  Use white vinegar in the rinse aid compartment of your dishwasher to 
help keep your dishes from getting spotty. I also fill the dishsoap section of my dishwasher with a lid with straight Lemishine.  Lemishine really is the KEY.
I got this recipe from 
The Lady with the Red Rocker, and she includes a price breakdown to show how much money you save by using this rather than store bought stuff.  Good luck, and happy dish washing!