I think anything whose soles are really thin and not too hard. I'm partial to Xero, but there's a lot of possibilities.

I do think all shoes, except those original Vibram Five Fingers, are not a great substitute for barefoot running itself. Running barefoot on a nice grass field feels so much nicer and more fun, too! But the minimal shoes do help force you to feel the ground and not just slam into it, so I think they can help.

Whatever you do, I'd only make changes slowly: try 10 minutes of barefoot running or with different shoes, a couple times a week at the end of a normal run, and go from there.