The powergrips are on this page of the Nashbar catalog:
http://www.nashbar.com/results.cfm?category=108&subcategory=1077&storetype=&estoreid=&init=y&pagename= . My sweetie uses them and likes them. The mini toe clips and ATB toe clips on that page look good.
I searched www.Bicycling.com , www.roadbikereview.com , www.nashbar.com , and www.HarrisCyclery.com and just could not find a technical article that develops the ideas, so you will have to go with my short explanation. I think cycling shoes are an excellent idea because they are stiff and preserve the energy of your stroke that would otherwise be lost. You could buy any of a number of cycling shoes and achieve that. Cycling shoes often feature a cover to keep your shoelaces from getting into the chainworks. They should have a "smooth" design with nothing to catch on when sliding into the clips.
Some other DU forum user may have a better idea of what to shop for. Those forums at www.bicycling.com were pretty darn interesting. Just try to resist getting drawn into them. :)
http://forums.bicycling.com/eve/forums