I am using the free version of the Hal Higdon Half-marathon training plan right now, training for the Rock and Roll race in St. Louis in October. Prior to starting this plan I have run only 5K's, so the half is an exciting goal for me.
I am finding it very useful and practical. The times in relation to the distances are a bit 'optimistic' for me. I'm slow! So, HH will say "run 4 miles, 40 minutes". I am pretty much ignoring the times and going for the distances.
I reach my first 5 mile run this weekend, and am signed up for a race that distance. Unfortunately it is going to be hot and humid, so I am certain to be walking some parts of it. Plan to use it for 'going the distance' and heat training.