Here is a great way to fill an empty corner. Build these corner bookshelves using these free woodworking plans.
This tiered corner plant stand is beautiful as well as functional. At this link you will find plans you can download to build one of these plant stands.
This is a link to a Google 3D SketchUp drawing for a corner plant stand suitable for indoors or out. Holes can be cut to allow plant containers to recess into bottom or left flat.
Here is a corner shelf unit with six shelves, made out of a single sheet of plywood. Free building instructions at the link.
This corner cupboard is built using mostly traditional methods – mortise-and-tenon joints for the face frame and door frame, a raised-panel door, tongue-and-groove backboards, and moldings to decorate the cabinets top and bottom.