Maybe you already have a nice patio table and need additional seating or perhaps you have a balcony too small for a table. If either of these are the case, consider turning a planter into an umbrella stand; you'll have a handy base for your patio umbrella and grow decorative plants or perhaps a mini-herb garden.
Outdoor living magazine Sunset recommends turning a large planter into an umbrella stand by filling the bottom of the planter with crushed lava rock, the middle with concrete, and the top with potting soil. Before doing this, get a black plastic ABS pipe that's large enough to fit your umbrella pole inside and run this from the bottom of the planter to a few centimetres above the potting soil. Don't worry, when you have plants growing, they will hide the pipe and having it backed up by lava rock and concrete will make the umbrella withstand all but tornado winds.
The cost of the project will vary depending on the umbrella and planter you choose, but you're probably in the $US100-$US200 range.