LURunner....
Nike Free Run (8-ish oz) is a good place to start as you get the benefit of foot strengthening and natural motion without an extreme shift from most standard training shoes. Free Run heel/toe offset is 7.2mm vs. 10-12mm of most trainers.
Your other option is Nike 3.0 (6.5-7oz) which is even more minimalist and as close as Nike gets to true barefoot. Offsets are 4mm which gets you in the range of many 3K-5K racing flats.
Which you choose is a matter of personal preference and what your body is conditioned to adapt to. If you have a lot of racing/training miles in racing flats then the 3.0 won't feel too extreme. Be smart regardless of which you choose and gradually increase your weekly mileage in Nike Free. 0 to 50 miles in a week or two in Nike Free is not recommended.