Joe, I really like the new balance 790, it is called a lightweight trail shoe, looks like a racing flat but has a harder plate on the bottom for trails. almost no heel, weighs maybe 7 ounces. This is my favorite shoe and I got several pairs on clearance for under 50 dollars with free shipping at new balance outlet online. works well on river trail and single tracks for me as well as on the road. Unfortunately, new balance discontinued it i think, like they do every good shoe they design. don't know what the replacement is. Paul likes this shoe as well and wrote a review of it here
http://www.thefinalsprint.com/2008/01/tfs-shoe-review-new-balance-mr790-trail-running-shoes/.
Lets go running up river trail one day this week and I will show them to you. Scott