The 2009 Niagara Icewine Festival will be held Jan. 17th, 18th, 24th and 25th in the Niagara region of southern Ontario. (The event is listed as spanning Jan. 16th - 25th, but the main events fall on the two weekends listed.) The official festival guide can be found here.
Every year the Icewine Festival features two outdoor icewine bars furnished with chairs and tables made out of ice (pics here). Sound interesting? Don't bother. Every year the icewine bars are crowded into tiny little tents not fit for the enormous volume of patrons crowding into them.
Each year that I've attended the Icewine Festival I've pushed and elbowed my way into the icewine bar located in the middle of the street in Niagara-on-the-Lake, only to wait in an extremely long line inside the tent for a sip of icewine that I won't get to enjoy to its full because someone will hit my elbow and make me spill half of it. Then I won't be able to enjoy any of the potentially interesting ice chairs because they are always--trust me, always--taken by people who are going to be sitting in them for a very long time.
My recommendation is that you go to the wineries themselves. You'll find shorter lines, friendlier service, cozier atmospheres and no crowds. A map of all the Niagara wineries can be found here. See p. 14ff. of the festival guide for a listing of events that will be taking place at each of the area wineries.
If you're in the area but can't make the Icewine Festival, consider coming out to the Niagara wineries during their "Days of Wine and Chocolate" weekends during Feb.
Ontario icewine is a unique and interesting beverage. If you can't make it to Ontario, look for icewine in the dessert wine section of your local wine shop or ask your wine retailer to order some for you. You won't be disappointed.