With Windows 8 almost released, we should see a whole slew of new multi-touch monitors, but not yet. My recommendation this year has been the Acer T231H - I have two of them reviewed them at http://njnnetwork.com/2012/04/review-acer-t231h-touch-monitor/.
They are a tad hard to find but they are still available. Unless you are in a desperate hurry, wait until October. Cheers, Stephen