Over here, in Winterland, most people use silicone grease on the seals so they don't stick. It's a lot less messy than a spray and does the job really well. But as Templar said, maintaining your seals with a good rubber treatment is the ideal way of dealing with this.
Oh, and NEVER force the door open when this happens! You will damage something, be it the seal or some door hardware. You can use a pan of warm (not hot!) water to free it, or a hair dryer (depending on where it is frozen in)... then wipe any water from the surface of the seal afterwards, of course.
It's funny to see that you guys are having about the same temperatures as us this year... which means it's unusually warm here for a change.
