For dingy items, add one cup of Cascade automatic dishwashing powder (not gel), 1/2 cup Arm & Hammer Super Washing Soda and a heaping measure of your normal laundry detergent to the wash cycle. Allow the agitation to begin, then turn the machine off. With the lid closed, allow the load to soak overnight. In the morning, turn the machine on and complete the cycles.NOTES: I've used store brand dishwashing powder for this and the Washing Soda is available at grocery or discount stores. It works best with a small load.
On a related topic, this recipe for homemade laundry detergent from the Complete Woman site looks interesting.