Harvest Moon has lovely panini sandwiches and salads. They have at least six vegetarian options on the menu plus a daily special that is always vegetarian or vegan. For vegans, the options can be somewhat limited. I would think the best bet would be to order off of their custom sandwich menu or ask them to not put dairy on some of the vegetarian sandwiches on the menu. There is now a second location in Bangor.
Cons: not many veg options, can be a bit slow