An airline stock, a workflow technology stock, and a housing materials stock make up a list of great value stocks to buy now.While the market isn't looking particularly cheap right now, you can inevitably find pockets of value. Delta Air Lines (DAL 1.99%), positioning and workflow-technology company Trimble (TRMB 1.02%), and building-materials company Owens Corning (OC -2.36%) fit the bill. Here's why.Delta Air Lines is the pick of the airline stocksWhether you are looking at its price-to-earnings (P/E) rat ...