Quote from mechimellow:

At Walgreens there is a product called Sinu-cleanse

That's what I bought and used. It really works too. It is a bit expensive initially, about $10, but once I finished that off I use the bottle and make my own saline solution. This bottle squirts up into your sinuses, as you lean over the sink and squeeze the bottle. It doesn't go down your throat, it doesn't feel like you are drowning, and it doesn't burn if you make your own saline mixture. It just goes up and you just relax and it dribbles back out. For a while I'd squeeze my nose and then lean completely over upside down to get the stuff alllll the way up in there. Then go back upright and allow it to drain in the sink. Then blow gently. I had a sinus infection for over six months, had taken a total of three rounds of antibiotics, a round of steroids, a round of decongestants, plus Allegra-D and Flonase for four months. And it STILL wouldn't go away completely. I bought the Sinu-Cleanse thing when I was at my wits end. It totally loosened up all that gunk and it was so gross. But it got most of that gunk out.
There is a thread in the Allergy section where many have tried the upside down sinus flooding using a saline mixture and some peroxide. I personally tried it and that burned and everything clogged up worse for a few days. So what I did was take two cups of water (filtered or distilled), one half teaspoon kosher salt or pickling salt, one half teaspoon of baking soda, that makes my saline mixture that I still use daily. It should taste like tears and it doesn't burn because it's supposed to be just like your natural tears and mucous. I got this recipe off a dr.'s website who is in Austin, I found this site doing a google search for peroxide sinus infection. When I still had brown and green gunk, I would add one teaspoon of peroxide and do the upside down flooding. It worked for me, after a six month long ordeal, my snot finally became clear and not solid colored and I was dancing a jig.
I also took Nettle herb, papaya extract and Goldenseal/Echinacea. You can find this information doing a search for sinus infection irrigation, various ENT's recommend irrigation and I found a dr. recommending the herbs above.
There's also a recommended product called Alkalol that you dilute at one half of this with saline and flood your sinuses. I used that a lot too, and it helped.
I tried a lot of things and I couldn't tell you what one thing worked, maybe a combination of all. I was just very desperate and if someone told me that bouncing on one leg while saying the Star Spangled Banner backwards while blinking my eyes would heal me, I might have tried it! LOL
But that is just my personal experience, and what worked for me. I found out after the fact that what I might have had was a fungal infection. All I know is that it's long gone now.