I know someone posted about a week ago asking about the dearth of interesting grapes around here, so I thought I'd give a heads-up. I just got some very sweet and tasty muscat grapes (from Chile, I believe) at the Prospect Street Bread & Circus in Cambridge. No idea if the other locations have them. They're mostly seedless, or rather the seeds are barely developed, and I thought real Muscats had fairly prominent seeds, so these may be some sort of hybrid.
They're rather pricey at 3.99/lb., but a nice treat.