I suffer from sinus problems pretty much year round, twice now had treatment for a nasal polyp over the past year or so. The one thing that has really surprised me with its effectiveness is the sea water nasal spray stuff you can get in cans from the pharmacy. Does an amazing job of clearing the sinuses. I tend to slightly ignore the instructions and snort it a bit then try and leave it in there for a bit before blowing it all out. Used two to three times a day it seems to work better than drugs at clearing the sinuses but of course it won't stop ones nose from running or getting blocked again if there is a root cause to the problems.
http://www.sterimarnasal.co.uk/