In the absence of a dedicated home office, the next best option is to carve out some space out of another room. The most popular target? The living room, since it's a centrally located "daytime" space that keeps work from bleeding into the bedroom.
IKEA expedit bookshelf, custom cut top shelf, add some crown molding for good looks. Make a little office, or an open closet for the hallway. Or as reading nook in kids room or headboard for the bed! Or a sewing room!