4.5 miles one-way, the Diamond Park trail is either an easy, rolling climb along a mountain stream with gorgeous views of the mountains and the lucious wildflowers, and/OR its a speedy downhill that flows and just begs to be shredded at top-notch! It's harder to take in the views on the way down, but it's totally worth it!
Seedhouse Trailhead
http://www.singletracks.com/item.php?c=1&i=7286