I agree, sudafed works well. But I would also agree with the note of caution struck in some of the posts. Ephedrine or pseudoephedrine a drug that athletes regularly get banned for, it is a banned stimulant in many fields.
For what it's worth, I take a sudafed (or two) during the day and if I am still suffering blocked sinuses, I will pop to the chemist and buy a small tub of menthol chrystals (about £1) and breathe them in over some hot water.
And if that doesn't work, I don't go to work.