(Vermicomposting Horse Manure by A.B. Card, J.V. Anderson and J.G. Davis).
Briefly, the concept is to use red wigglers to turn your horse manure into compost. I thought this would be a great experiment to try at my brother's horse farm. The web article above presents 2 options; we used option 1 in which aged horse manure is placed into a windrow and seeded with red wigglers.
We started on September 10, 2006 with about 5 pounds of red wigglers. As shown in the photo below, this is likely too few worms for the amount of horse manure used, but it is a start. Note that 5 pounds of red wigglers will cost approximately $100.
UPDATE - April, 2007: Steve reported that he has harvested some beautiful black soil for his garden from the windrow. They also see many wild turkeys picking through the windrows could they be eating the worms???
UPDATE - August, 2007: Steve reported that the windrows have been a success. He has been able to manage his manure better with less runoff.