I come across men's denim workjackets a lot at estate sales, and have always loved them. They're like denim 49ers: simple shape, casual and unlined, but best of all they usually have big patch pockets on the front.
It's just a great knocking around jacket, something that's a favorite to toss over an outfit like to one shown above, but I can picture it with a gauzy floral dress too. And layers in the winter, over wool and plaid.
They also make a linen version if you want something more summer specific, but my workwear weakness makes this one a winner.