I guess I'm kind of lucky that I'm a big imposing guy so people don't laugh at me. I have an old green canvas bag of some sort that fits my netbook and other stuff that I carry like my ibuprofin (I hurt a lot), hair brush, liter bottle of iced tea, and crap like that. It does NOT look like a purse but I call it my "murse": man-purse. I really don't care what people think of it, its convenient to throw my crap into it when I go places.
If I had the money, I would not mind a "European Shoulder Bag" that looks nice.