Whether it's a sinus infection or a cold or other virus, try one of these:
Place about 5 drops of Eucalyptus in a coffee cup of hot water. Cover your head with a towel, CLOSE YOUR EYES, and sniff the vapor for a few minutes. (You can also just cup your hands around the top of the mug and sniff through an opening in them.) Or sniff (as above) or diffuse any of the Carvacol-rich oreganos and rosemary, cineole. This combination won't just clear your sinuses; it will also kill the bacteria, etc. up in there that could be causing the trouble. It may take 48-72 hours for the full effect to be felt.
Why yes, I did finally come down with my kids' virus, what made you ask? :) (Actually left the house this morning without trying any preventative measures, knowing I was getting the crud. By 5pm I was running a temperature, so I headed home and took Ibuprofen and made my first attempt at using oregano to fight a virus. So far, I'm impressed, but we'll see how I feel in the morning.