I managed to get some barefoot running in while I was off in Illinois and Ohio. My callouses are thickening up quite nicely.
One thing that has been helpful is Chi Running. This book has made a world of difference in my running technique. I no longer get blisters because I'm much better at landing and lifting my feet with minimum motion and no pushing off. More importantly, I'm running with what feels like less effort. Basically I run like I did when I was a kid.
Here's what I think is a good explanation most people can relate to. Remember what a child does when she first starts to walk? The body leans forward. Gravity wants to pull the body down but the child puts a foot underneath their hips to prevent that. Then they repeat the process with the next foot and continue until they reach their destination. That's basically how I run now, but without the pacifier and diaper. Instead of stepping forward, I just keep my feet under my hips while my body slightly leans forward. There's more to it besides that, but that's the essential part.
In the past I would go out and run 2-4 miles and that evening I would feel it. My quads might be a little sore and my energy level would be down. Running was a necessary evil that I tolerated for the fitness and health benefits. Now I can go out at lunchtime and run just over 4 miles every day with impunity. My legs aren't sore and I still have plenty of energy the rest of the day. But the main difference is I now enjoy running.
And the barefoot part? It's not necessary, but it sure is fun.