Antibiotics do a pretty lousy job of treating sinus infections. I've been on 2 rounds this year alone (Levaquin & Avelox).
If sinus problems are the result of an obstruction or physical defect (deviated septum, bone spur, polyp, etc.), surgery is required to correct the problem. Most sinus problems fall into this catagory, and virtually all "chronic" problems have an obstruction componant.
Home remedies include irrigation and steam masks, but if your problem is chronic, you are looking at surgery.
I've had some nasty side-effects from Avelox, including muscular pain and carpal tunnel syndrome (which I hope will go away).