Plenty of solid recommendations in here, but nobody has mentioned the best answer -- Barrette's Hardwood, which is just over the border in Thompson, CT. They specialize in domestic hardwoods. You'll have a range of widths and thicknesses to choose from, and pretty much everything is dimensioned. They also have a staggering selection of live edge wood as well if you're interested in that. Their prices are higher than the other suppliers I use for my business (Goosebay Lumber and Highland Hardwoods, both in NH), but they have by far the best overall selection in the Worcester area.